Article No. : 18

My Bio & Scientific Articles [HERE]

Update Date 1 :

INDEX

1. Introduction.

2. Physical Reasons of Flight.

3. History of Airfoil.

4. Airfoil Performance.

5. Applications of Airfoil.

6. Future Technologies of Airfoil.

7. Benefits of CFD Simulation Programs.

8. CFD Simulation of The Miracle Airfoil.

9. Conclusions

10. Last Words.

11. References & Websites.

Acronym:

RAE: Royal Aircraft Establishment @ UK.

NASA: National Aeronautics & Space Agency @USA.

NACA: National Advisory Committee for Aeronautics (By NASA).

ARMD: Aeronautics Research Mission Directorate (By NASA.)

CFD: Computational Fluid Dynamic.

GAMBIT: Geometry And Mesh Building Intelligent Tool (By ANSYS Inc.)

 FLUENT: It’s just a phrase suggested by Brilliant English Scientist physicist  Sir: Isaac Newton in one of his technical treatises on flow when relating the word to flowing fluids he suggested it’s use for smooth flows & it’s now the name of CFD software by ANSYS Inc.

1) Introduction

Professionals in aviation industry still believe (& agree in quorum), that there is no way for any new concept for designing a wing which is differ from traditional one, due to the simple idea of Bernoulli’s phenomenon which stated that the air speed on upper part should be higher than lower part to generate lift (Pressure Difference) on plane. And if it’s happen & find another concept, it will be a scientific breakthrough & will open a new chapter in aviation generation book.

Figure (1) – Why planes can fly? Bernoulli’s concept is one of the answers.

Speaking of which, there are 2 concept (until now) which are mainly depend on lifting/flying objects (e.g. birds & planes) & they are:

1. Bernoulli’s Concept of Fluid Motion.
2. Boundary Layer Concept.

Two months ago, I found a new revolutionary concept while I was testing new designs of wing/airfoil by using Pre-processing program named “GAMBIT” & CFD simulation program named as  “FLUENT” which both belongs to ANSYS Inc. & I have positive results after hard learning by myself to understand how we can simulate a wing like NACA 2412 perfectly & evaluate the lift & drag coefficient with considering the important factors such as y-plus (Y+) which is related to the turbulence flow.

Figure (2) – Pressure Contour of NACA 4412 Airfoil

This numerical breakthrough of 3^rd concept will lead to increase the efficiency of flight by decreasing a huge amount of total mass of planes which consequently make a fuel consumption more economical up to 65%. Also, the prominent feature of miracle airfoil that It doesn’t affect by flow regions (e.g. incompressible, subsonic , … etc)

(3) – Douglas DC-8 producing contrails at a bio-fuel test

In our extraordinary analysis article, we will discuss how planes & birds fly & mention briefly the history of wings with it’s applications & know some of recent developments of wing. Then we will show the numerical results of our CFD simulation  for different cases & types of wing without disclosing the secret design.

2) Physical Reasons of Flight

We said previously, that there are 2 concepts which depend on flying objects, which are:

1. Bernoulli’s Concept of Fluid Motion.
2. Boundary Layer Concept.

Bernoulli’s effect is obvious to people who studied physical science or mechanical engineering. For simplicity, it’s stated that if the speed of air/water is decreased by increasing the duct/pipe, so the pressure will increase consequently by somehow, & the vice versa is true. Figure (4) shows what I’m talking clearly.

Figure (4) – Bernoulli’s Law

Definitely, we are talking if the density of air is constant & if not, the ideal gas law will involved which mean that the temperature should be involved in our equations to take it’s effect on Bernoulli’s concept.

In general speaking, Bernoulli’s concept has a relation with energy conservation by somehow.

Anyway, let us talking about the 2^nd strange concept called “The Boundary layer”

Many graduates engineers (like me !) think that Bernoulli’s concept was the only factor which is making planes & helicopter to fly above the ground.

I was always asking myself;

1) Does it really changing the speed of air between upper & lower part of wing may lead to generate a lift force by creating difference of pressure ?

2) What’s really happen between air particles & surface of wing in the micro-scale ?

Bernoulli’s concept doesn’t give you a full vision of what happen between the molecules.

After I read very informative, understandable, interesting, & exciting book named by “ Fundamentals of Aerodynamics, 5^th Edition “ by Dr. John D. Anderson, Jr., my previous knowledge has been changed totally.

Figure (5) – Cover of the Book

You may download a PDF file from [HERE]

When an object (e.g. plane) move inside a large volume of fluid (gas/liquid), there will be 2 distinct layer which surrounded the object. The thick layer will have a same speed in all points along the perpendicular line of the surface of object. So, this region has been characterized by frictionless feature & named as “Inviscid Region”.

The another region is named as “Viscous Region” which is adjacent to the surface of object & it has a very thin layer. The velocity of fluid on this region changed along the perpendicular line of surface from Zero (on surface) to maximum value which is equal to the velocity on the in-viscid region. So, the 2^nd region has velocity gradient due to molecules friction. Figure (6) shows those types of region.

Figure (6) – Viscous and inviscid Region

The common property with these regions that it have the same pressure points along the perpendicular line of object’s surface.

Maybe you will surprise, if you know that the thin layer of viscous region are responsible of lift for planes.

Let us read what Dr. Anderson say in his informative book:

Without Friction, Could We Have Lift?

In Section 1.5 we emphasized that the resultant aerodynamic force on a body immersed in a flow is due to the net integrated effect of the pressure and shear stress distributions over the body surface. Moreover, in Section 4.1 we noted that lift on an airfoil is primarily due to the surface pressure distribution, and that shear stress has virtually no effect on lift. It is easy to see why. Look at the airfoil shapes in Figures 4.17 and 4.18, for example. Recall that pressure acts normal to the surface, and for these airfoils the direction of this normal pressure is essentially in the vertical direction, that is, the lift direction. In contrast the shear stress acts tangential to the surface, and for these airfoils the direction of this tangential shear stress is mainly in the horizontal direction, that is, the drag direction.

Hence, pressure is the dominant player in the generation of lift, and shear stress has a negligible effect on lift. It is for this reason that the lift on an airfoil below the stall can be accurately predicted by inviscid theories such as that discussed in this chapter. However, if we lived in a perfectly inviscid world, an airfoil could not produce lift. Indeed, the presence of friction is the very reason why we have lift.

These sound like strange, even contradictory statements to our discussion in the preceding paragraph. What is going on here? The answer is that in real life, the way that nature insures that the flow will leave smoothly at the trailing edge, that is, the mechanism that nature uses to choose the flow shown in Figure 4.18c, is that the viscous boundary layer remains attached to the surface all the way to the trailing edge. Nature enforces the Kutta condition by means of friction. If there were no boundary layer (i.e., no friction), there would be no physical mechanism in the real world to achieve the Kutta condition.

So we are led to the most ironic situation that lift, which is created by the surface pressure distribution—an inviscid phenomenon, would not exist in a frictionless (inviscid) world. In this regard, we can say that without friction we could not have lift. However, we say this in the informed manner as discussed above. [Ref-1]

Although I don’t yet convinced, but I should read more about it extensively when I have time.

Anyway, you can find more detail in that  exciting book that I have mentioned earlier.

I promise that you will enjoy it.

3) History of Airfoil:

Anybody interested in aviation industry, definitely knows who are the “Wright’s Brothers”.

They are an American Inventors who built the 1^st  operated airplane with successful sustained flight in 17 Dec 1903.

Figure (7) – Wright’s Plane

Figure (8) – Wright’s Plane

That’s accomplishments don’t come without cost.

Failure experiments, deep knowledge, hard working & beautiful patient were the key factors of succession.

Figure (9) – Stages of Development for Wright’s Plane

Since their 1901, glider was of poor aerodynamic design, the Wrights set about determining what constitutes good aerodynamic design.

In the fall of 1901, they design and build a [ 6ft long x 16inch square ] wind tunnel powered by a two-bladed fan connected to a gasoline engine. A replica of the Wrights’ tunnel is shown in Figure (10).

In their wind tunnel they test over 200 different wing and airfoil shapes, including flat plates curved plates, rounded leading edges, rectangular and curved plan forms, and various monoplane and multi-plane configurations. A sample of their test models is shown in Figure (11). The aerodynamic data are taken logically and carefully.

Figure (10) – Replica of the wind tunnel designed – Wrights Brother

Figure (11) – Wing models tested by the Wright brothers in their wind tunnel during 1901–1902

Armed with their new aerodynamic information, the Wrights design a new glider in the spring of 1902. The airfoil is much more efficient; the camber is reduced considerably, and the location of the maximum rise of the airfoil is moved closer to the front of the wing.

The most obvious change, however, is that the ratio of the length of the wing (wingspan) to the distance from the front to the rear of the airfoil (chord length) is increased from 3 to 6.

                                                        Figure (12) – Wing Area of Different Planes   

The success of this glider during the summer and fall of 1902 is astounding; Orville and Wilbur accumulate over a thousand flights during this period. In contrast to the previous year, the Wrights return to Dayton flushed with success and devote all their subsequent efforts to powered flight.

The rest is history. [Ref-1]

So, the starting point of aviation industry was in 1903 & we still understand aerodynamics very well every day especially by using computer software by using CFD approach to analyze the flow of air over wing.

Definitely, there were many attempts by different means & ways to fly & below are figures which shows one of them:

Figure (13) – Leonardo da Vinci’s Ornithopter design

Figure (14) – Governable parachute” design of 1852

Figure (15) – Jean-Marie Le Bris and his flying machine, Albatros II, 1868

Figure (16)  – The Aeroplane of Victor Tatin, 1879.

Figure (17) – Otto Lilienthal, May 29, 1895.

Figure (18)  – Santos-Dumont’s “Number 6” rounding the Eiffel Tower in the process of winning the Deutsch de la Meurthe Prize, October 1901

 [You may download a PDF file of Aviation History from HERE]

Figure (19-A)  – Poster of Book talking about Abbas Ibn Firnas

Abbas Ibn Firnas was very creative engineer and inventor who successfully constructed the first flying machine. His flying machine was controlled one and he also demonstrated it’s flight, many centuries before designs of Leonardo Da Vinci. He is also famous for developing a glass lens that could be used to correct some vision problems. He had done many inventions and is so famous that a crater on the moon has been named after his name. [web-1]

Figure (19- B) – Abbas Ibn Firnas

With his flying machine he jumped off a cliff and stayed a loft for 10 minutes. Unfortunately he couldn’t land as  smoothly and injured his back during his crash. This mistake made him realize how important the tail of a bird is for landing. To honor his accomplishments, Baghdad’s northern airport is named after him as well as a bridge in Cordoba (Spain) and a moon crater.[web-2]

Figure (19- C)- -Statue of Ibn Firnas outside Baghdad International Airport

Figure (19- D) Bridge in Cordoba (Spain)

Anyway, after 1903, we have the ability to fly, but in that decades, the design of wing/airfoil was depend by luck. It was based on guessing & imagination . It wasn’t organized in a uniform system.

Early airfoils were designed by trial and error. Royal Aircraft Establishment (RAE), UK and Gottingen laboratory of the German establishment which is now called DLR(Deutsches Zentrum fϋr Luft-und Raumfahrt – German Centre for Aviation and Space Flight) were the pioneers in airfoil design. Clark Y airfoil shown in Fig.(1) is an example of a 12% thick airfoil with almost flat bottom surface which has been used on propeller blades. [Ref-2]

Figure (20)- View of RAE Location

Figure (21) – Douglas Dakota III, ZA947, Royal Aircraft Establishment (RAE)

So, in 1930, the National Advisory Committee of Aeronautics (NACA) developed an organized system for airfoil design.

NACA was a U.S. Federal Agency founded on March 3, 1915, to undertake, promote and institutionalize aeronautical research. That’s was born date of airfoil series 4-digit in first place.

Figure (22) –Logo of NACA

“ The early NACA airfoil series, the 4-digit, 5-digit, and modified 4-/5-digit, were generated using analytical equations that describe the camber (curvature) of the mean-line (geometric centerline) of the airfoil section as well as the section’s thickness distribution along the length of the airfoil. Later families, including the 6-Series, are more complicated shapes derived using theoretical rather than geometrical methods.

Before the National Advisory Committee for Aeronautics (NACA) developed these series, airfoil design was rather arbitrary with nothing to guide the designer except past experience with known shapes and experimentation with modifications to those shapes. This methodology began to change in the early 1930s with the publishing of a NACA report entitled The Characteristics of 78 Related Airfoil Sections from Tests in the Variable Density Wind Tunnel. See figure (23). [Ref-3]

Figure (23) – The Variable Density Wind Tunnel (VDT)

The VDT was operational in October 1922 at the NACA Langley Memorial Laboratory at Hampton, Virginia. It is essentially a large, subsonic wind tunnel entirely contained within an 85-ton pressure shell, capable of 20 atm. This tunnel was instrumental in the development of the various families of NACA airfoil shapes in the 1920s and 1930s. In the early 1940s, it was decommissioned as a wind tunnel and used as a high-pressure air storage tank. In 1983, due to its age and outdated riveted construction, its use was discontinued altogether. Today, the VDT remains at the NASA Langley Research Center; it has been officially designated as a National Historic Landmark. (Courtesy of NASA.) [Ref-1]

In this landmark report, the authors noted that there were many similarities between the airfoils that were most successful, and the two primary variables that affect those shapes are the slope of the airfoil mean camber line and the thickness distribution above and below this line.

Figure (24) – Wing Geometry Definitions

They then presented a series of equations incorporating these two variables that could be used to generate an entire family of related airfoil shapes. As airfoil design became more sophisticated, this basic approach was modified to include additional variables, but these two basic geometrical values remained at the heart of all NACA airfoil series. [Ref-3]

Any airfoil in NACA series has a specific terms (e.g. length & thickness) to construct the airfoil according to the corresponding number (digit). As we see in figure (25),the geometry of airfoil is consist of such terms:

• The Chord.
• Maximum thickness.
• Maximum thickness position.
• Maximum Camber line.
• Maximum camber position.

Figure (25) – Airfoil Nomenclature

Let us know what’s the mean of NACA 4-Digit for airfoil an example (e.g. NACA 2415).

The first family of airfoils designed using this approach became known as the NACA Four-Digit Series.

The first digit specifies the maximum camber (m) in percentage of the chord (airfoil length), the second indicates the position of the maximum camber (p) in tenths of chord, and the last two numbers provide the maximum thickness (t) of the airfoil in percentage of chord.

For example, the NACA 2415 airfoil has a maximum thickness of 15% with a camber of 2% located 40% back from the airfoil leading edge (or 0.4c).

Utilizing these m, p, and t values, we can compute the coordinates for an entire airfoil using the following relationships. [Ref-3]:

Figure (26)

where

x = coordinates along the length of the airfoil, from 0 to c (which stands for chord, or length)

y = coordinates above and below the line extending along the length of the airfoil, these are

either yt for thickness coordinates or yc for camber coordinates

t = maximum airfoil thickness in tenths of chord (i.e. a 15% thick airfoil would be 0.15)

m = maximum camber in tenths of the chord

p =position of the maximum camber along the chord in tenths of chord

Figure (27) shows a different shapes of NACA 4-digit series.

Figure (27) – Many Shapes of NACA 4-Digit Series

There are many digit series of NACA which they are:

• NACA 4-Series.
• NACA 5-Series.
• Modified NACA Four- and Five-Digit Series.
• NACA 1-Series or 16-Series.
• NACA 6-Series.
• NACA 7-Series.
• NACA 8-Series.

Figure (28) shows the difference of them with other model of airfoil.

Figure (28) – Different model of airfoil

Now let us see what’s the pros & cons of each series which is represented in figure (29).

Figure (29) – Pros & Cons of NACA Series

Today, airfoil design has in many ways returned to an earlier time before the NACA families were created. The computational resources available now allow the designer to quickly design and optimize an airfoil specifically tailored to a particular application rather than making a selection from an existing family. [Ref-3]

That’s true, using powerful computers with simulation software (e.g. Fluent-ANSYS ) may help us to predict the flow of air over any complicated shape of wing approximately more accurate than real experiment which is waste our time & money but definitely we can’t ignore the real experiment in our life because it’s the actual place to invest our money.

Figure (30) – taken from NUMECA website

• NASA airfoils

NASA has developed airfoil shapes for special applications.

For example GA(W) series airfoils were designed for general aviation aircraft.

The “LS” series of airfoils among these are for low speed (LS) airplanes. A typical airfoil of this category is designated as LS(1) – 0417. In this designation, the digit ‘1’ refers to first series, the digits ‘04’ indicate C lopt of 0.4 and the digits ‘17’ indicate the thickness ratio of 17%. Figure (31-e) shows the shape of this airfoil.

For the airfoils in this series, specifically designed for medium speed airplanes, the letters ‘LS’ are replaced by ‘MS’(see Fig.31.f).

NASA NLF series airfoils are ‘Natural Laminar Flow’ airfoils.

NASA SC series airfoils are called ‘Supercritical airfoils’. These airfoils have a higher critical Mach number. Figure (31-g) shows an airfoil of this category.

Figure (31) – Typical Airfoil

• Airfoil selection

Large airplane companies like Boeing and Airbus may design their own airfoils.

Figure (32) – Specifications of  Airbus & Boeing Plane

However, during the preliminary design stage, the usual practical is to choose the airfoil from the large number of airfoils whose geometric and aerodynamic characteristics are available in the aeronautical literature.

To enable such a selection it is helpful to know the aerodynamic and geometrical characteristics of airfoils and their nomenclature. [Ref-2]

Figure (33) – Boeing 737 Airfoil Sections

Figure (34) – Boeing 737 Airfoil Sections

That’s the reason why there are an extreme competition between manufacturing companies of planes to find reliable, strong & light design of wing which is reflected positively in the economical side for airlines companies to attract more clients by offering the best solutions for their commercial or military purposes especially by making the fuel consumption more cost effective.

Figure (35) – Manufactures are competed hardly to win the race of aviation industry

4) Airfoil Performance:

The important factors in flight are Drag, Lift Coefficient, angle of attack (AoA) & Lift-Drag Ratio.

Lift (L) is defined as the component of the aerodynamic force that is perpendicular to the flow direction

Drag (D) is the component that is parallel to the flow direction

So, the coefficient of drag & lift can be calculated as we see in figure (36) & (37) respectively.

Figure (36) – Drag Equation of Plane

Figure (37) – Lift Equation of Plane

Angle of attack (α) : It’s angle between relative wind and chord line of airfoil as we see in figure (38).

Figure (38) – How Measuring the Angle of Attack on Plane

Stall Angle: A stall occurs when the angle of an airfoil exceeds the value which creates maximum lift as a consequent of airflow cross it. See figure (39) for more understanding.

In fluid dynamics, a stall is a reduction in the lift coefficient generated by foil as angle of attack increase. This occurs when the critical angle of attack of the foil is exceeded.

Figure (39) – Effect of Stall on Airfoil

Lift-Drag Ratio: is the ratio between the lift to drag coefficient @ specific angle of attack (AoA).

Figure (40) shows the curve graph of both drag & lift coefficient in polar style with corresponding angle of attack (AoA).

Figure (40) – Polar curve and L/D to AoA curve

An aircraft designer does not only have to make sure that enough lift is produced by the wings but also at a reasonable amount of thrust, i.e. without simultaneously producing too much drag. We can see that C_D has its minimum value at small angles of attack.

As the stall angle is approached, the drag increases at a progressively higher rate due to separated flow.C_D has its minimum value at small angles of attack. With an increase in the AoA, drag increases at a progressively higher rate.

In order to evaluate the wing efficiency we must consider more than just the lift produced. In fact, a wing has its greatest lifting ability just prior to the stalling angle of attack. Unfortunately, near the stalling angle, the wing also generates considerable drag.

A wing has its greatest lifting ability (C_Lmax) at the stall AoA but also very high induced drag. The minimum drag occurs at a fairly low angle of attack, in this case slightly above zero degrees AoA. Unfortunately, the lifting ability is very low at low angles of attack.

At each angle of attack, the lift/drag ratio is the ratio between lift and drag or between the coefficient of lift and the coefficient of drag. It expresses the aircraft efficiency. [Ref-4]

   Figure (41) – Highest L/D ratio in Polar Curve

When I was able to simulate NACA 2412 successfully, I was wondering always from where did people find this old fashioned & nasty graph of real experiment of NACA airfoil which shown in figure (42) as example ?

   Figure (42) – Data of Lift & Drag coefficient for NACA 4412

Tried hardly day after day & suddenly, when I was downloaded PDF files from internet, I find the answer.

It was from  “Abbott Report” or it officially named as “NACA Report 824” which is issued in 1945.

It has everything that I want for NACA 4digit series experimental results.

Figure (43) – Cover of NACA Report 824 “Abbott Report”

I was in relief to compare my simulation with real one to see how close I’m from the accuracy for NACA 2412/4412.

You may download it from [HERE] especially if you’re interested with CFD Simulation of airfoil.

The camber of airfoil also has it’s effect on lift & drag coefficient. Figure (44) & (45) shows that difference.

Figure (44) – Effect of airfoil camber on lift coefficient

Figure (45) – Effect of airfoil camber on drag coefficient

Many engineers are interested in designing high lift systems for planes.

So, Why High Lift is Important ?

Figure (46) – Mechanism of High Lift Systems Control

• Wings sized for efficient cruise are too small to take-off and land in “reasonable” distances.
• From Boeing: ”

– “A 0.10 increase in lift coefficient at constant angle of attack is equivalent to reducing the approach attitude by one degree. For a given aft body-to-ground clearance angle, the landing gear may be shortened for a savings of airplane empty weight of 1400 lb.

– “A 1.5% increase in maximum lift coefficient is equivalent to a 6600 lb increase in payload at a fixed approach speed”

– “A 1% increase in take-off L/D is equivalent to a 2800 lb increase in payload or a 150 nm increase in range.”

• For fighters: – Devices move continuously for minimum drag during

maneuvering.

• Powered Lift concepts hold out the hope for STOL operation. [Ref-5]

STOL: Short Takeoff & Landing

There are many designs for high lift configurations as we see in figure (47).

Figure (47) – Miscellaneous Design of High Lift Systems

Boeing has been developed the high lift system since 1947. Figure (48) shows the phases of change for wing design.

Figure (48) – Trends in Boeing Transport High Lift System Development

Figure (49) – Boeing 747-100

Imagine how the shape of slat & flap may effect in the value of maximum lift coefficient as we see in figure (50).

Figure (50) – Effect of adding slat & flap in airfoil

Figure (51) – Airbus 380 Trailing Edge Flap System

Figure (52) shows a curve graph of highest lift of airplanes manufacturers. RJ70 plane has high value among other planes which the lift coefficient is approximately equal to 3.5

Figure (52) – Coefficient Maximum Lift Data of Airplane Manufacturers

I think there is nothing to write here.

Definitely there are more detail about performance like momentum , center of pressure & other stuff, but … we don’t think it’s important for our case.

5) Applications of Airfoil:

Far as I know, there are few applications that depends on airfoil & they are:

1. Wings for planes.
2. Propellers.
3. Rotor Blades. (e.g Helicopter)
4. Turbine blades.

Figure (53) – Application of Airfoil

So, the industries which is depend on the airfoil are:

• Aviation Industry.
• Renewable Energy Industry (Wind Type).
• Power Generation Industry.

Figure (54) – Industries depend on Airfoil

There is also another industry could be added to that list which is a “Maritime’ but it’s limited to used it.

Airfoil in that scope of industry is named as “Hydrofoil” which it has the same function of airfoil, but we will used in water instead of air. Hydrofoil will be attached to ships & submarines similar to the plane’s wing.

   Figure (55) – Layout of Ship with front hydrofoil

   Figure (56) – Ship with Hydrofoil

So, why I said it’s limited to used in the maritime industry.

We know that increasing the speed of boat or ship will lead to move the boat upward due to the relationship between viscosity, external force & velocity gradient.

   Figure (57) – Viscosity effect on Speed of Boat

Now, if we use hydrofoil inside water, the upper part of it will have higher velocity rather than the lower part as we knew from Bernoulli’s effect. Obviously, the pressure in that upper part will reduce to some value which lead to convert the water into vapors as we see in figure (58) . This phenomenon called “Cavitation”.

Figure (58) – Cavitation occur in upper part of hydrofoil

Cavitations is defined as the phenomenon of forming and imploding vapor bubbles in a region where the pressure of the liquid falls below its vapor pressure. Cavitation and the resultant damage can occur in any fluid-handling equipment, especially in pumps. See figure (59)

Technological advances in industrial protective coatings and composite repair materials have made it possible to repair pumps operating in a cavitating environment rather than simply replacing them after damage occurs. [Web-3]

Figure (59) – Negative Effects of Cavitation on Tools & Equipments

When you see the speed list for different types of ships like in figure (60), you will wonder about how very low speed of ship in upper part of hydrofoil may cause cavitation phenomenon.

Figure (60) – List of speed for different types of ships

The answer is found in the density. For air & water, it’s 1.2 Kg/m³ & 1000 Kg/m³ respectively.

Anyway, there is a draft paper of mine suggested 10 ideas to solve the cavitation issue. Some of them wanted to run CFD simulation software for analyzing & evaluating the new design of hydrofoil.

I don’t have time yet for them. So, maybe in the future will be published.

6) Future Technologies of Airfoil:

The accumulation knowledge over years is the key for making an excellent design for anything.

Understanding the philosophy of nature & how it’s act on specific conditions for unique design, will let us to improve it next time.

Why learn about aerodynamics?

For an answer, just take a look at the following five photographs showing a progression of airplanes over the past 70 years.

The Douglas DC-3 (Figure 61-A), one of the most famous aircraft of all time, is a low-speed subsonic transport designed during the 1930s. Without a knowledge of low-speed aerodynamics, this aircraft would have never existed.

The Boeing 707 (Figure 61-B) opened high-speed subsonic flight to millions of passengers beginning in the late 1950s. Without a knowledge of high-speed subsonic aerodynamics, most of us would still be relegated to ground transportation.

The Bell X-1 (Figure 61-C) became the first piloted airplane to fly faster than sound, a feat accomplished with Captain Chuck Yeager at the controls on October 14, 1947. Without a knowledge of transonic aerodynamics (near, at, and just above the speed of sound), neither the X-1, nor any other airplane, would have ever broken the sound barrier.

Figure (61)

The Lockheed F-104 (Figure 62-A) was the first supersonic airplane point-designed to fly at twice the speed of sound, accomplished in the 1950s.

The Lockheed-Martin F-22 (Figure 62-B) is a modern fighter aircraft designed for sustained supersonic flight. Without a knowledge of supersonic aerodynamics, these supersonic airplanes would not exist.

Figure (62)

Finally, an example of an innovative new vehicle concept for high-speed subsonic flight is the blended wing body shown in Figure (63). At the time of writing, the blended-wing-body promises to carry from 400 to 800 passengers over long distances with almost 30 percent less fuel per seat-mile than a conventional jet transport.

Figure (63)

This would be a “renaissance” in long-haul transport. The salient design aspects of this exciting new concept are discussed in Section 11.10. The airplanes in Figures (61–63) are six good reasons to learn about aerodynamics. [Ref-1]

Recently, there are a lot of developments in aviation industry has been applied & some of them still test phase in different scope such as airframe, engines & alternative fuels.

We will briefly talk about some of these developments here in my article & you may read the rest of it from PDF file named as  “IATA Technology Roadmap : Technology Annex” which is Prepared in collaboration with the Aerospace Systems Design Laboratory (ASDL), Georgia Institute of Technology.

You may download it from this website  [HERE].

So, let us see some of the next generations of aviation industry maybe found in the future.

1) The Morphing Airframe:

In the longer-term future, it is conceivable that an aircraft would reconfigure its aerodynamic surfaces “on the fly” to achieve maximum performance during each element of the flight profile.

Key enablers for this significant gain in adaptation capabilities, in conjunction with flight controls and mission objectives that exploit the ability to drastically morph, are:

1. Materials capable of supporting flight loads and undergoing high strain without creep.
2. Compact actuators consuming exceptionally low power, yet are able to generate substantial forces and displacements. The use of piezoceramic actuators as well as adaptronics technology is under consideration.

The aerospace industry is currently investigating the practicality of morphing structures that combine smart materials and compact actuators. For instance, the USAF/NASA/Boeing Active Aeroelastic Wing (AAW) programme’s objective is to control the twist of a flexible wing in to induce roll movements, thereby obviating conventional roll-control surfaces that are mechanically complex [40].

The Morphing Aircraft Structures (MAS) programme of the US Defense Advanced Research Projects Agency (DARPA) involves the development of multiple vehicular platforms by Lockheed, Raytheon Missile Systems, and NextGen Aeronautics. The program’s primary emphasis is on realizing the technological feasibility of large-scale, in-flight morphing. Lockheed’s Z-wing concept has a seamless folding structure to provide conformal coverage over the wing-fold area at each fold. The seamless skins are made out of elastomers produced through the vacuum assist resin transfer mold (VARTM) process. The wing folds itself through hierarchically mechanized servo-drive systems, locked by fold brake systems once folding is achieved.

Figure (64) – The Morphing Shape of NASA

Figure (65) – The Material Structure of Morphing Airframe

Figure (66) – N-MAS wind tunnel model -left- morphing structure layout (center), and elastomeric skin with ribbons (right)

MIT and NASA Engineers Demonstrate A New Kind of Airplane Wing

Assembled from tiny identical pieces, the wing could enable lighter, more energy-efficient aircraft designs

A team of engineers has built and tested a radically new kind of airplane wing, assembled from hundreds of tiny identical pieces. The wing can change shape to control the plane’s flight, and could provide a significant boost in aircraft production, flight, and maintenance efficiency, the researchers say.

Figure (67) – The Morphing Plane on Subsonic Tunnel

The new approach to wing construction could afford greater flexibility in the design and manufacturing of future aircraft. The new wing design was tested in a NASA wind tunnel and is described today in a paper in the journal Smart Materials and Structures, co-authored by research engineer Nicholas Cramer at NASA Ames in California; MIT alumnus Kenneth Cheung SM ’07 PhD ’12, now at NASA Ames; Benjamin Jenett, a graduate student in MIT’s Center for Bits and Atoms; and eight others.

Instead of requiring separate movable surfaces such as ailerons to control the roll and pitch of the plane, as conventional wings do, the new assembly system makes it possible to deform the whole wing, or parts of it, by incorporating a mix of stiff and flexible components in its structure. The tiny subassemblies, which are bolted together to form an open, lightweight lattice framework, are then covered with a thin layer of similar polymer material as the framework.

The result is a wing that is much lighter, and thus much more energy efficient, than those with conventional designs, whether made from metal or composites, the researchers say. Because the structure, comprising thousands of tiny triangles of matchstick-like struts, is composed mostly of empty space, it forms a mechanical “metamaterial” that combines the structural stiffness of a rubber-like polymer and the extreme lightness and low density of an aerogel.

Figure (68) – Morphing Plane Manufactured by Tiny pieces of lighter Material

Jenett explains that for each of the phases of a flight — takeoff and landing, cruising, maneuvering and so on — each has its own, different set of optimal wing parameters, so a conventional wing is necessarily a compromise that is not optimized for any of these, and therefore sacrifices efficiency. A wing that is constantly deformable could provide a much better approximation of the best configuration for each stage. [Web-4]

Figure (69) – The Future of Morphing Airframe

2) Hybrid-Wing-Body :

The hybrid or blended wing body (BWB) concept originated at McDonnell Douglas in the late 1990s in response to the question posed by NASA’s Dennis Bushnell, “renaissance for the long-haul transport?” [119] Initial iterations of McDonnell Douglas’ and the Boeing Company’s BWB designs indicated a 25% reduction in per-seat fuel burn over an 800 passenger-conventional, tube-and-wing configuration [120, 121].

Figure (70) – The Hypothetical Design of Blended Wing Plane

Subsequent studies have focused on aircraft concepts ranging from 200 to 600 passengers. The most recently studied concept, which is funded under NASA’s N+2 Subsonic Fixed Wing program, is a 300-passenger replacement for the Boeing 777. NASA design efforts indicate that the BWB configuration alone produces a 10% fuel burn saving comparable to a B777-200ER with GE90 engines on a 7,000 nautical mile mission carrying a full passenger load. The aerodynamic benefits are larger for very big BWB aircraft. However, an 800+ seat BWB has a wingspan of 90 to 100 meters. This is incompatible with today’s airport compatibility rules, which limit aircraft size to 80 meters length by 80 meters span. The BWB shape that is totally different from today’s aircraft also generates a number of other airport operations issues that need to be solved. Another main unsolved issue is pressurization of a big lens-shaped cabin.

A significant amount of research has been performed in this area by Boeing. The Silent Aircraft Initiative is a venture between the University of Cambridge and the Massachusetts Institute of Technology, and within the European research projects VELA and NACRE.

The current generation of the Silent Aircraft Initiative, the SAX-40, has focused on developing an aircraft configuration that would provide a 20% reduction in fuel burn) over current generation commercial transports, and limit the perceptual noise, commonly taken to include a Day-Night Noise Level greater than 55dB, to within the perimeter of a typical international airport [123].

Figure (71)

While the BWB appears attractive on paper, the technology is relatively immature. Thus far, only subscale demonstrators, including the Boeing X-48, have been flight-tested [124]. Significant design, maintenance, and airport compatibility issues must be addressed, all of which may delay the commercialization of the BWB to beyond the 2020 timeframe. Nevertheless, the U.S. military has expressed interest in the concept as either a transport aircraft or an aerial refuelling tanker [125] and NASA and other organizations are continuing the technology risk reduction programme.

3) Cruise-Efficient Short Take-off and Landing (CESTOL):

The Cruise-Efficient Short Take-off and Landing (CESTOL) concept was devised to provide a capability to perform missions of around 1000 NM, similar to the majority of flights performed today by the Boeing 737 and Airbus A320 families of aircraft, while operating from smaller regional and “metroplex” (city) airports. These have stringent demands for low noise and short and/or steep climb and descent requirements [126].

Figure (72) – The Hypothetical Design of CESTOL Concept

The CESTOL is a response to NASA’s Horizon Missions Methodology (HMM) [127]. Under the HMM, it is envisaged that there will be a shift in airline network structures toward a more distributed framework [128]. This would decrease the average number of passengers carried on an individual flight. Moreover, these passengers would desire to operate out of local airports closer to home, which are often not equipped with runways or facilities capable of handling larger aircraft. A CESTOL aircraft, on the other hand, could operate on runways as short as 500 metres and cruise at Mach numbers near those of current generation civil transports [129].

An advantage of the CESTOL concept, even when operating in larger airports, is that the aircraft would be able to operate in and out of runways that, at present, can only be used by small regional jets and turboprops. This would relieve many existing airports from congestion, and thus reduce the fuel burn associated with taxiing and holding. This is only an operational fuel saving, since a CESTOL aircraft’s fuel burn per passenger-km might be rather higher than for current ones.

4) Truss and Strut-braced Wing (TSW/TBW):

Beginning with the inception of the Boeing 707, nearly all modern subsonic transport aircraft bear a close resemblance to one another in their external configurations. Along with continued investigations on several revolutionary configurations, such as the Blended Wing Body and the Joined Wing [130], the Truss-Braced Wing (TBW) [131] concept has been recognized as another alternative subsonic configuration that could considerably enhance the aerodynamic efficiency of a conventional take-off and landing aircraft.

Figure (73) – Boeing SUGAR Truss-Braced Wing (TBW) Aircraft Concept

The motivation toward the TBW configuration is grounded on the well-known relationship between induced drag and wing aspect ratio. Extensive increases in the aspect ratio or wingspan would yield a considerable reduction in drag, thereby enhancing the lift-to-drag ratio during cruise. Nevertheless, this idea is not likely to be realized with conventional cantilever wings due to weight penalties. Wing weight increases with increasing wing aspect ratio, thus negating any gains associated with improved aerodynamic efficiency, such as savings in fuel weight, from an aircraft perspective.

            Figure (74) – TBW Pressure Coefficient Distribution Computed by STAR-CCM+

However, the TBW concept would allow a substantial increase in wingspan with few significant weight penalties, or in some cases, savings in wing weight are likely [132]. Such aerodynamic enhancement at little structural cost would further serve to reduce wing area and aircraft weight according to a general aircraft sizing routine. Additionally, the resultant downsizing of the propulsion system would, in turn, allow a synergistic reduction in noise emissions levels. A recent study [133] on Strut-Brace Wing configurations, which can be considered as a subset of the TBW, indicates that an optimized single-strut configuration can allow a nearly 20% reduction in take-off gross weight and a 29% reduction in fuel burn when compared to a technologically similar cantilever-wing configuration [134,135]. Such remarkable improvements in cruise performance would logically enable nominal reductions in pollutant engine emissions. These benefits, which originate solely from aerodynamic enhancements, would be further augmented if appropriate supporting technologies were to be synergistically integrated into a working TBW concept.

Figure (75) — Notional Diagram of TBW with VCCTEF System

A TBW configuration designed for civil transport is most likely to have a very long wingspan, possibly larger than the gate-box limit of 80 meters. This is why a folding wing concept, similar to that applied to the Boeing 777 as an optional feature, is considered to be one of the core enablers for the TBW aircraft. Such extremely high aspect ratio wings, however, are a cause of significant unknowns with respect to the ability to manufacture and maintain TBWs. Further, the additional weight of the wing folding mechanism will reduce and possibility eliminate the fuel burn benefit. There is ongoing research at NASA that focuses on risk reduction related to the TBW concept.

5) Boundary Layer Ingesting Inlet:

Recent trends in the development of engine nacelles and engine/nacelle integration have focused on reducing the interference losses, fuel burn (~3.8 % based on Silent Aircraft [60]) and minimizing noise. However, there are several potential developments in nacelle design that promise not only to reduce noise, but also to mitigate engine installation losses. These technologies include the buried, boundary layer ingesting installation concepts shown in Figure (76) and the variable area fan nozzle.

Figure (76) — Boundary layer ingesting inlets Concept

Motivated by the drive to create a silent aircraft, designers have been investigating burying and/or shielding the propulsion system from the external flows. This typically involves placing the engine inside the fuselage or the wing, or putting a portion of the vehicle’s structure between the engine and an observer.

Figure (77) – Sketch of Working Principle of BLI concept

The issue here is that the body of the vehicle disrupts the flow. In the past, either an engine’s inlet was located outside of the boundary layer, or the disturbed air was diverted, as it contributed to losses in efficiency.

Figure (78) – Boundary layer ingesting inlets on Aircraft

The boundary-layer ingesting inlet, on the other hand, is devised to re-energise the wake of the aircraft [59] by ingesting the incoming boundary layer.

Figure (79) – Boundary layer ingesting inlets Fan

The downside of this concept is that the distortion of the airflow occurs at the engine fan face, which has the potential to decrease fan efficiency and increase the stress on the fan blades [60, 68]. It is therefore doubtful if this design principle can be made beneficial for modern engines.

6) Slotted, Natural Laminar Flow (SNLF) Airfoil:

Figure (80) – SNFL Airfoil merged with TTBW Concept

The research is targeted to address ARMD Strategic Thrust 3 –Ultra-Efficient Commercial Vehicles.

By demonstrating a viable aerodynamic wing-design concept enabling 70% reduction in fuel/energy burn compared to 2005 baseline. The solution is by a Revolutionary Airfoil Design: called “Slotted, natural-laminar-flow” (SNLF) airfoil.

Figure (81) – SNFL Airfoil Design

Non-experts will be able to see the difference.

This unique design of airfoil have these features:

• Low-speed tests show simultaneous decrease in cruise drag coefficient and increase in static maximum lift coefficient.
• Slotted airfoils also have known benefits for transonic wave drag.
• Changes the rules for airfoil design and affords extra degrees of freedom.

Figure (82) – SNFL Airfoil in Lab

Figure (83) –  S414 installed in the Penn State Low-Speed, Low Turbulence Wind Tunnel

Figure (84) – CFD Result of SNFL Airfoil

Figure (85) – CFD Result of SNFL Airfoil

A multidisciplinary team of researchers covering all areas of aeronautics (Primarily academic partners (UTK + 5 others) with 2 two industrial partners (Airfoil, Incorporated + Boeing Research & Technology).

Figure (86) – Partners of this exciting project

• Build upon recent N+3 concept studies by Boeing and MIT where natural laminar flow is an enabling technology for performance goals. Down-selection to Boeing TTBW configuration.[Ref-6]

Figure (87) – Testing SNFL Airfoil merged with TTBW concept in wind tunnel

Figure (88) – Boeing SUGAR High TTBW

You may read about this technology by downloading PDF File from [HERE]

7) Span-wise Adaptive Wing (SAW):

Figure (89) – Span was used to decrease the drag of air

NASA is exploring the feasibility of a system that will allow part of an aircraft’s wing to fold in flight, to increase efficiency through wing adaptation.

Engineers at NASA’s Armstrong Flight Research Center in California, Langley Research Center in Virginia, and Glenn Research Center in Ohio, are working on the Span-wise Adaptive Wing concept, or SAW.

Figure (90) – Small Prototype of Plane with SAW concept

Figure (91) – Small Prototype of Plane with SAW concept

Figure (92) – Technical Detail of ARENA Plane Prototype

The concept, if feasible, would permit the outboard portions of the wings to move to the optimal position during operation. This could potentially result in an increase in efficiency by reducing drag and increasing lift and performance.

Figure (93) 

Through advanced actuation, SAW aims to use control surfaces to allow the outboard portions of wings to adapt as much as 75 degrees, to optimally meet the demands of the various conditions throughout a flight. A mechanical joint, acting as a hinge line for rotation, makes the freedom of movement possible.

Figure (94) – Span can rotate 75⁰ Degree

“Ideally, we would be able to take that portion of the wing, and articulate it up or down to the optimal flight condition that you’re in,” NASA Armstrong principal investigator for SAW Matt Moholt said.

 “So let’s say you’re a condition that requires a climb-out. The optimal position might be up 15 degrees or down 15 degrees, and you would be able to get that.”

The objectives of testing on PTERA include the development of tools and vetting of system integration, evaluation of vehicle control law, and analysis of SAW airworthiness to examine benefits to in-flight efficiency.

Figure (95) – Future Plane may changed totally by Applying SAW concept

The ability to achieve an optimal wing position for different aspects of flight may also produce enough yaw control to allow for rudder reduction on subsonic and supersonic aircraft, which may provide additional benefits to aircraft efficiency, such as reduced drag and weight. [Web-5]

You may watch the video of SAW concept [HERE].

That’s all what I have for this exciting space. You may find more in IATA  PDF link.

IATA has uploaded a video for promising technologies that will be in the market between 2035 – 2050. You may watch the video [HERE].

7) Benefits of CFD Simulation Programs:

Figure (96) – Life without computer

No doubt that entering the era of computer changed everything in our life.

The old engineers definitely remembered what the life look like in the past, when they were drawn or do a complicated experiment without helping the Auto-CAD or Simulation software.

Figure (97) – Old days of drawing

Figure (98) – Old days of drawing

Figure (99) – Old days of drawing

Really, it was hard time which nobody can imagine now.

Using computer makes our life more easy, flexible & accelerated our business by using Internet.

Figure (100) – 3D Simulation of Flight

There are many types of simulation software either in mechanical , civil, electrical , chemical & so on.

For the simulation of wing, we used a CFD software such as “Fluent-ANSYS”.

Fluid (gas and liquid) flows are governed by partial differential equations which represent conservation laws for the mass, momentum, and energy.

Computational Fluid Dynamics (CFD) is the art of replacing such Partial Differential Equation (PDE) systems by a set of algebraic equations which can be solved using digital computers.

Computational Fluid Dynamics (CFD) provides a qualitative (and sometimes even quantitative) prediction of fluid flows by means of:

• Mathematical modeling (partial differential equations – PDE)
• Numerical methods (discretization and solution techniques)
• Software tools (solvers, pre- and post-processing utilities)

CFD enables scientists and engineers to perform ‘numerical experiments’ (i.e. computer simulations) in a ‘virtual flow laboratory’

Numerical simulations of fluid flow (will) enable [Ref-7]:

• Architects to design comfortable and safe living environments.
• Designers of vehicles to improve the aerodynamic characteristics.
• Chemical engineers to maximize the yield from their equipment.
• Petroleum engineers to devise optimal oil recovery strategies.
• Surgeons to cure arterial diseases (computational hemodynamics).
• Meteorologists to forecast the weather and warn of natural disasters.
• Safety experts to reduce health risks from radiation and other hazards.
• Military organizations to develop weapons and estimate the damage.
• CFD practitioners to make big bucks by selling colorful pictures.

These are some of examples of capability of CFD can do in our life.

Figure (101) – Simulation of AC-1 Aircraft

Figure (102) – Applications of CFD Simulation

Figure (103) – Applications of CFD Simulation

CFD model demonstrating the correlation between wall shear stress (WSS) and restenosis in coronary artery disease (a – structural modeling of sent insertion in porcine arteries reconstructed from micro-ct and stent-srtery coupling obtained after arterial recoil (See figure 104–A)

Comparison between the in vivo histological images (left) and corresponding sections from structural simulation (right) demonstrating excellent agreement (See figure 104-B).

Figure (104) – CFD Simulation for Coronary Artery Disease

Results of CFD simulation in terms of the spatial  distribution of WSS magnitude over the arterial wall. (See figure 104-C)

The correlation between areas characterized by low WSS (orange lines) an in-stent restenosis after 14 day. The CFD simulation of WSS has identified areas of reduced shear and restenosis with excellent agreement. (See figure 104-D) [LINK]

So, what’s the difference between simulation & real experiment.

The answer in below figures.

Figure (105) – Difference between Experiment & Simulation

Figure (106) – Difference between Experiment & Simulation

Now, let us see our results of miracle airfoil by using CFD program “Fluent”.

8) CFD Simulation of Miracle Airfoil:

⊕⊕ Preparation stage

Before we begin, I should mention something embarrassing about me that I had done it in the past related to CFD Simulation.

In 2018, I have published an article named as “Fuel Consumption Mitigation of  Aircrafts by Applying Astonishing Ideas” & I have used Simulation program “Fluent-ANSYS”as you see in figure (107).

Figure (107)

In that dark time, I had no idea totally about:

1. The value of Y-plus “Y+” for turbulence flow & how it’s crucial factor in CFD simulation especially for
2. The Angle of attack (AoA).
3. The types of NACA series.
4. The NACA experimental results (Abbott NACA report 824) for comparing.

I was thinking that, I may draw any shape of airfoil by using pre-processor drawing program such as “GAMBIT” & then use CFD simulation such as “Fluent” to see the results.

Then, I will add my creative ideas on it as we see in figure (108) & see any further improvements in the performance of airfoil such as drag & lift force.

Figure (108) – My first idea in that old article

Simple, isn’t ?

You may read & know these ideas here [Article].

When I started this simulation of miracle airfoil (which I was thought that I fulfilled by enough knowledge of how to simulate an airfoil successfully such as NACA 4412 & I did it), I was made another mistake.

Figure (109) – Meshing NACA 4412 by using GAMBIT Software

Figure (110) – Contours of Static Pressure of NACA 4412 using FLUENT Software

Figure (111) – My CFD Residuals of NACA 4412

Figure (112) – Comparison of my CFD Simulation with Abbott Report

I was thinking that if I have very low residuals by reducing the Courant Friedrich-Levy (CFL) number, that should mean more accurate results. The new airfoil is complicated, so by using normal ways will not give us result unless an CFD error, so either it’s non-physical case or the mesh is low .

The last issue of enhancing mesh will take a long time to see results [see figure (113)] which I don’t prefer it for preliminary designs for quick evaluating & analyzing to see if it’s good or not & after that if there is high powerful computer we can increase the mesh quality.

Figure (113) – Required Time for increasing the accuracy of simulation

So, how I discover the mistake ??!!

One day, I have downloaded some PDF files related to CFD simulation & I found a paper/presentation named as “Lecture 5 – Solution Methods Applied Computational Fluid Dynamics by Instructor: Prof. André Bakker”.

You may read about it by downloading PDF File from Bakker’s website [HERE]

I went through it to see what it was containing from information & I noted something strange.

He said [See Figure (114)]:

Figure (114)

What ?? Residuals are not my solution !!!

I was shocked.

Why lowering residuals doesn’t mean more accurate answer. That’s weird really.

He also said [See Figure (115) ]:

Figure (115)

I will not deny that I had my doubts about my obtained results of miracle airfoil as there are some tolerance fluctuations in range of ±0.001  as we see in figure (116), but I said to myself: “Maybe it’s matter of mesh quality”

I have used coupled – pressure based solver as the remain option (e.g. SIMPLEC) was not helpful & also the coupled didn’t give me an answer unless to reduce the CFL number up to 0.1 & I was thinking I’m brilliant 🙂

Figure (116) – My Previous mistake about Simulating Miracle Airfoil

Under-relaxation factor (URF)or Courant Friedrich-Levy number (CFL) are tricky mathematical method to stabilize the iterative process. It shouldn’t be too low. When stabilizing returned back, then we can change gradually the value of URF or CFL up to default value.

We always learning from our mistakes to improve our ability to be familiar with new knowledge.

⊕⊕ Launching stage

Obviously, I can’t reveal the secret design of miracle airfoil for future business & sign Non-Disclosure Agreement (NDA) with companies who are interested with this innovative concept & scientific breakthrough in aviation industry.

Figure (117) – Confidentiality is A Business Treasure

So, we will give only the results of CFD simulation with real screenshots from the window of “Fluent” program to authenticate my expertise that everything is fine.

We will study all situations of air flows which is related to Mach number (Ma) & they are:

1. Incompressible Flow. (Ma <3)
2. Subsonic Flow. (0.3< Ma <8)
3. Transonic Flow. (0.8< Ma <2)
4. Supersonic Regime. (1.2< Ma < 5)
5. Hypersonic Regime. (5< Ma < 12)
6. Hyper Velocity Flow (12< Ma)

Figure (118) – Mach Number Flow Regimes

I should also mention that I have discovered many designs for the 3^rd concept (e.g. Type A,B, C, …), which means more flexibility in designing process  when our options is limited according to the operating conditions.

So, let us start our investigation with first type.

Miracle Airfoil – Type “A”

#1# Incompressible Flow (Ma < 0.3) Case:

We have used GAMBIT software to draw the miracle airfoil with it’s boundary layer which the length of boundary should be 20 time of the airfoil’s cord to use “Pressure Far-Field” option in boundary condition for compressible flow case later. See figures (120) & (121).

Figure (120) – Meshing Miracle Airfoil  type “A” using Gambit Software

Figure (121) – Boundary Condition of Miracle Airfoil  type “A” in FLUENT Software 

Below Figure shows our case properties parameter that has been used for our simulation for incompressible flows cases of type “A” in Fluent software:

Figure (122) – Solver Properties in FLUENT Software

Figure (123) – Viscosity Properties in FLUENT Software

For incompressible flows it is normal to specify a large (typically atmospheric pressure) operating pressure and let the solver work with smaller “gauge” pressures for the boundary conditions, to reduce round–off errors. [Ref-8]

Figure (124) – Material Properties in FLUENT Software

Figure (125) – Solution Control Properties in FLUENT Software

Figure (126) – Residuals Properties in FLUENT Software

I have started with air velocity of 60m/s (Ma = 0.173) in the beginning of this simulation, and I will not deny that I encounter many issues for obtaining stability status until I used an adaption for increasing the mesh quality.

Figure (127) – Inlet Properties in FLUENT Software

Figure (128) – Outlet Properties in FLUENT Software

Definitely, that’s option has an expensive cost on the required time to simulate the miracle airfoil successfully. It can takes days to get CFD results even you are using low turbulence option like Spalart-Allmaras model.

Figure (129) & (130) shows the residual plot & iteration values of type “A”.

Figure (129) – Residual Plot of Type “A” by FLUENT Software

Figure (130) – Iteration Values of Type “A” by FLUENT Software

You may notice that, how the values of drag & lift coefficient seems approximately constant in range of 10^-3. That’s agree of what Prof. Baker said previously to obtain an accurate answer of our case as we see in figure (131). Lift & drag coefficient are important factors to decide that.

Figure (131) – Prof. Bakker’s Statement about accurate result

The detail of lift & drag force (pressure + viscous) is shown in figure (132).

Figure (132) – Lift & Drag Force of Type “A” by FLUENT Software

For making sure that the quality of mesh has not any effect on our CFD result, we used double precision (DP) option in fluent & we have these results shown in figures (133) & (134):

Figure (133) – Double Precision Option activated for Residuals Plot

Figure (134) – Double Precision Option activated Iteration Values

As we see from figure (134), the values @ normal & double precision (DP) option in Fluent software are very close to each other. So, we are in good hand with Fluent & we can use normal precision to save time for all situations.

We have also tested our miracle airfoil – type “A” with another models to make sure that it’s doesn’t effect by changing the classical models which based on Reynolds Averaged Navier-Stokes (RANS) equations (time averaged). The main models in CFD Fluent Software are shown in figure (135). The number of equations denotes the number of additional Partial Differential Equations (PDEs) that are being solved.

Figure (135) – Turbulence Models in FLUENT

We have used only 2 model which are: RKE & K-Omega SST model. Below Figures shows the result of residuals & iteration values which contains the drag & lift coefficient @ normal precision.

Figure (136) – Residual Plot of Type “A” by using RKE model

Figure (137) – Iteration Values of Type “A” by using RKE model

Figure (138) – Residual Plot of Type “A” by using K-Omega model

Figure (139) – Iteration Values of Type “A” by using K-Omega model

Actually, I don’t use Reynolds stress model, because if those previous models S-A, RKE or K-Omega takes me several hours to find accurate result due to the high quality of meshing that I have made by using Adaption option. So, how do you think it will take time to simulate by using Reynolds Stress. Look to figure (141) & you will see how much.

Figure (140) – Standard RANS models

Figure (141) – Advanced RANS models

Now let us see how miracle airfoil may affect with angle of attack (AoA) & different velocities f air in range of incompressible flow regime.

• Angle of Attack (AoA ) Effect:

We use the same velocity of previous example (e.g. V=60m/s) with normal precision option with Spalart-Allmaras turbulence model for Fluent software in our evaluation of how the miracle airfoil – type A  may act on AoA for ±2, ±4 & ±6 degree.

Remember that sign of angle represent the rotation of angle. Positive sign means, the angle will be calculated with the clockwise dircetio9n & vice versa is true.

AoA = +2⁰ @ V=60m/s

Figure (142) & (143) shows the residuals & iteration results for angle of attack (AoA) in respect of speed 60m/s.

Figure (142) – Residual Plot of Type “A”

Figure (143) – Iteration Values of Type “A”

AoA = +4⁰ @ V=60m/s

Figure (144) – Residual Plot of Type “A”

Figure (145) – Iteration Values of Type “A”

AoA = +6⁰ @ V=60m/s

Figure (146) – Residual Plot of Type “A”

Figure (147) – Iteration Values of Type “A”

Now let see the effect of negative sign of angle of attack.

AoA = -2⁰ @ V=60m/s

Figure (148) & (149) shows the residuals & iteration results for angle of attack (AoA) in respect of speed 60m/s.

Figure (148) – Residual Plot of Type “A”

Figure (149) – Iteration Values of Type “A”

AoA = -4⁰ @ V=60m/s

Figure (150) – Residual Plot of Type “A”

Figure (151) – Iteration Values of Type “A”

AoA = -6⁰ @ V=60m/s

Figure (152) – Residual Plot of Type “A”

Figure (153) – Iteration Values of Type “A”

By collecting all the results of angle of attack effect in table comparison & draw a curve graphs, we will have what we see in below figures. Note, that angle of attack  equal to Zero (AoA=0⁰ Deg) has been tested in first example before.

Figure (154) – Comparison table for AoA effect on miracle Airfoil type A

Figure (155) – AoA Effect on Lift Coefficient   

Figure (156) – AoA Effect on Drag Coefficient  

Figure (157) – AoA Effect on Lift/Drag Ratio  

• Speed Effect:

We have tested different speeds of air in the range of incompressible flow (e.g. 5, 50, 60 & 100m/s) to see if the lift or drag coefficient has been changed. But there is no change at all.

Here’s the results of our simulation for miracle airfoil – type “A”.

V=5 m/s @ AoA = 0⁰ Deg

Figure (158) & (159) shows the residuals & iteration results for speed = 5m/s in respect of AoA = 0⁰.

Figure (158) – Residual Plot of Type “A”

Figure (159) – Iteration Values of Type “A”

V=50 m/s @ AoA = 0⁰ Deg

Figure (160) – Residual Plot of Type “A”

Figure (161) – Iteration Values of Type “A”

V=100 m/s @ AoA = 0⁰ Deg

Figure (162) – Residual Plot of Type “A”

Figure (163) – Iteration Values of Type “A”

By collecting all the results of speed effect in table comparison, we will have what we see in figure (164). As you notice, we don’t need to draw a graph curve to see the relationship between speed & coefficient values as it’s constant for all situation either laminar or turbulence flow.

Note, that speed of 60m/s @AoA=0⁰ Deg, has been tested in first example.

Figure (164) – Comparison table for speed effect on miracle Airfoil type A

• Thickness Effect: (Later)
• Special Length Effect: (Later)

#2# Subsonic Flow (0.3< Ma < 0.8) Case:

Figures (165) & (166) shows our case properties parameter that has been used for our simulation for subsonic flows cases of type “A” in Fluent software & as we know air will be compressible fluid which means we will use the idea gas law to determine pressure, temperature & density.

Figure (165) – Solver & Viscosity Properties in FLUENT Software

For compressible flows, the solver needs to use the absolute values in the calculation, therefore, with compressible flows, it is sometimes convenient to set to operating pressure to zero, and input/output “absolute” pressures.

Figure (166) – Material & Operating Pressure Properties in FLUENT Software

Figure (167) – Solution Control Properties in FLUENT Software

The pressure-based solver with the Coupled option for the pressure-velocity coupling is a good alternative to density-based solvers of ANSYS Fluent when dealing with applications involving high-speed aerodynamics with shocks. Selection of the coupled algorithm is made in the Solution Methods task page in the Solution step. [Ref-9]

I have started with air velocity of 200m/s (Ma = 0.5671) s a base point of comparison with other velocities with Spalarat-Allmaras turbulence model. Figure (168) & (169) shows the inlet & outlet parameters of pressure & temperature by assuming that total pressure & temperature is 101.325 KPa & 300 K.

Figure (168) – Inlet Properties in FLUENT Software

Figure (169) – Outlet Properties in FLUENT Software

Figure (170) & (171) shows the residual plot & iteration values of type “A” for velocity = 200 m/s .

Figure (170) – Residual Plot of Type “A” by FLUENT Software

Figure (171) – Iteration Values of Type “A” by FLUENT Software

I will be honest with you, that you can’t only start simulation & get result immediately as we see in above two figures even it seems not accepted for regular engineer as fluctuation appear in some residuals line especially the parameters of momentum equation, but when I saw a simulation of NACA 0012 with approximately same fluctuations, they get an accurate result for drag & lift coefficient as we see in figure (172) & (173). As Prof. Bakker said before, we should monitor the interest parameter that we concerned such as lift or drag coefficient.

Look how it’s very steady in right graph of figure (173).

Figure (172) – Convergence of NACA 0012 airfoil by FLUENT

Figure (173) – Residuals Fluctuation exist in that case

So, you should apply some tricks & tips in FLUENT software to stabilize & accelerate the solution with accurate result as possible as it can. Such ideas is to use the 1^st Order Upwind first until reach to converged situation, then switch to the 2^nd Order Upwind.

Also, I nearly forget to mention that one of methods to ensure & assess that you get an accurate result is to check the value of net flux of mass & heat of all inlet & outlet sides. Figure (174) shows what I’m talking about related to subsonic case.

Figure (174) – Mass Flux Net Result of Subsonic Case

From this example, you may notice that there is no significant difference in the lift & drag coefficient between subsonic & incompressible flow as we see in figure (175).

Figure (175) – Comparison between incompressible & subsonic case @ AoA= 0⁰ Deg

It’s the scientific or said numerical evidence that our miracle airfoil is unique & have more secrets to be disclosed especial the effect of special length.

Now let us see how miracle airfoil may affect with angle of attack (AoA) & different velocities f air in range of incompressible flow regime.

• Angle of Attack (AoA ) Effect: (Later)
• Speed Effect: (Later)
• Thickness Effect: (Later)
• Special Length Effect: (Later)

#3# Transonic Flow (0.8< Ma < 1.2) Case: (Later)

#4# Supersonic Flow (1.2< Ma <5) Case: (Later)

#5# Hypersonic Flow (5< Ma < 12) Case: (Later)

#6# Hyper Velocity Flow (12< Ma) Case: (Later)

Miracle Airfoil – Type “B” (Later)

Miracle Airfoil – Type “C” (Later)

Miracle Airfoil – Type “D” (Later)

9) Conclusions:

Miracle Airfoil- Type “A”

The main feature of miracle airfoil –type “A” that it doesn’t change the values of aerodynamic performance in all situation.

In our conclusions section we will compare previous result of miracle airfoil with recent airfoil corresponding to the flow situation (e.g. incompressible, subsonic , …etc) to see if it’s revolutionary technology or not.

Comparison 1: Incompressible Flow Situation

W have select NACA 4412 as standard airfoil to compare it with the miracle airfoil @ velocity of 60m/s. Figure (176) shows the aerodynamic performance (lift, drag, momentum coefficient) of NACA 4412 which has been plotted by using X-Foil software.  As you notice, the lift & drag coefficient are 1.5259 & 0.01350 @ AoA = 10⁰ Deg.

Figure (176) – Simulation Result of NACA 4412 by X-Foil Software

That angle of attack (AoA) is assumed to give higher lift coefficient for NACA 4412 according to the Abbott’s Report 824, as we see in figure (177). Maybe you will not see it Clearly unless you download the PDF report & zoom it.

Figure (177) – Practical Result of NACA 4412 by testing airfoil in Wind Tunnel

Anyway, it seems that miracle airfoil – Type A – can’t compete with the low speed applications as the lift-drag ratio of it was 4.3 which is lower than NACA 4412 which was 113 in maximum value of lift coefficient.

The road for discovering the secrets of miracle airfoil is too long as we should consider the effect of special length which I believe it will enhance the airfoil performance without forget that we are talking now only in type “A” .

So, we will continue our research in incompressible flow situation as soon as possible as I’m very excited for it & I hope that I have the time & high process CPU because it takes me long time to get results.

Figure (178) – The Journey Started

Let us see how really miracle airfoil effect the high speed application significantly.

Comparison 2: Subsonic Flow Situation

I have select Boeing as my standard comparison with miracle airfoil as it’s data available in many articles.

Figure (179) shows the curve graph of aerodynamic performance for “B787  Dreamliner” by using simulation software named as “PIANO”.

Figure (179) – Performance of B787 Dreamliner by PIANO Software

I found also a PDF file named as “Transonic Aerodynamics of Airfoils and Wings” which is contains a curve graph of performance for b747-100 as we see in figure (180).

Figure (180) – Comparison of approximate drag rise methodology with Boeing 747-100 – flight test data from Mair and Birdsall

It seems that they considered mach number of 0.6 or 0.7 as a transonic flow, not subsonic as I mentioned before. Definitely, this matters related to the shape of airfoil.

Anyway, we will assume that Ma=0.7 is in subsonic flow, & as you notice from last curve that all lines are horizontally steady before Ma=0.75, so we can assume that speed of 200 m/s (Ma = 0.5671) has the same aerodynamic performance (lift & drag coefficient) of point located in red circle.

Definitely, we will neglecting the effect of body & engine of B747-100 plane.

So, according to what I found about B747-100 in Webs, the mass of wings approximately equal to 40.2 ton as we see in the right column of figure (181).

Figure (181) – Weight Breakdown for some Representatives Aircraft

Figure (182) shows the aerodynamic performance & dimensional values of B747-100 airfoil & we compare it with the miracle airfoil – type “A”.

Figure (182) – Comparison between B747-100 & Miracle Airfoil

As you noticed, the mass of airfoil has been decreased up to 14 ton which means we have reducing fuel consumption by percentage of 65%. It’s excellent option for economic of companies & environmental sides for humankind.

Comparison 3: Transonic Flow Situation (Later)

Comparison 4: Supersonic Flow Situation  (Later)

Comparison 5: Hypersonic Flow Situation  (Later)

Comparison 6: Hyper Velocity Flow Situation  (Later)

10) Last Words.

1) Time:-

Figure (183)

As I remember, I have started this scientific research in September 2019 when I simulated new airfoils that I have imagined with different design by CFD simulation software named as  “Fluent-ANSYS”.

Suddenly, I found my treasure airfoil which can let us to reduce a significant amount of fuel consumption.

In that time, I wasn’t aware that this 3^rd concept of flight can really give us more flexibility options to choose what suitable for our situation. That’s the reason why there are many types of miracle airfoil such as type “A”, “B”, “C” & so on.

It will takes long time to evaluate these types by CFD simulation software with regular & limited personal computer, without mention that we should know exactly how each type reacted in different flow regions (e.g. incompressible, subsonic , ….etc)

We will be patient & maybe this new technology will be one of the greatest scientific breakthrough in history of aviation. I will not deny that I have some mistakes but with time I correct them.

I understand the reason of 3rd concept exactly & it will takes time to establish it’s theory.

2) Wind Tunnel:-

Figure (184)- Exterior Part of  Wind Tunnel

Numerical results (or CFD Simulation) is not enough for deciding to manufacture planes in commercial business line. We should test our design in what’s called “Wind Tunnel” to match the real life circumstances.

Figure (185) – Rocket placed in Wind Tunnel

Numerical results helps us to predict approximately preliminary behavior of what will happen in practical, but the final decision is coming from practical tests. So, the sequence of process is simple, starting with simulation, small prototype , then large prototype & finally the commercial manufacturing for safe use.

Boeing currently under contract with NASA to mature and develop the TTBW Concept. This is a continuation of previously-funded NASA Projects [Ref-6]:

• SUGAR Phase I –TTBW Conceptual design and technology roadmap
• SUGAR Phase II –TTBW Aeroelastic development (FEM and TDT test)
• SUGAR Phase III –High-speed design and test of a TTBW for Mcruise=0.745
• SUGAR Phase IV (in progress) which includes:

1. Development of high-speed lines for Ma_cruise=0.8
2. High-speed wind tunnel test
3. Low-speed (high-lift) system development
4. Low-speed (high-lift) wind tunnel test

Figure (186) & (187) shows the roadmap for NASA/Boeing Transonic Truss-Braced Wing (TTBW) project & I was wondering why testing prototype take many years to evaluate ?

Does it have a relation with priorities of funding budget?

Figure (186) – Project Plan

Figure (187) – Roadmap of Technology

Very few companies & institutions has this type of wind tunnel & we should wait until the professionals agree our numerical results & then we can move forward to test the 3^rd concept in small prototype & I will publish the results one-day.

Failure of My Laptop:-

Before Tuesday 27/Feb/2020, I was try to fix a micro-SD for someone which shows files but it can’t be deleted.

Actually, I lifted as it seems impossible to do anything about it by any partition software. But in that worst day in my life, I tried again & suddenly the laptop hang out, then screen turn on to blue. It was Dump memory Errror. Sometimes it’s called “The Blue Screen of Death” [See figure 188]

Figure (188) – The Screen of Death

I said to myself “It happened before a lot & I should wait until the countdown finish”.

When the computer restart, the screen turn on black. [See figure 189]

Figure (189) – The Black Screen issue

Really I was shocked.

I was searching on internet to find the solution & I realized what happen.

My Laptop’s disk has been in RAW state. The machine can’t find the operation system of  windows in disk as it’s not organized.

The worst nightmare that nobody like to hear/see it at all. Everything (files & scientific  researches) worked since 2013 is gone now because I should format it.

Figure (190) – The Horrible Nightmare of People

All that happen due to small micro-SD card. small piece ruin my whole Laptop.

But the life may let us to find the hope by using bootable partition or recovery software.

On 5 March 2020, I solved the issue by converting the RAW to NTFS (e.g. FAT16 & FAT32) only without formatting & loosing data. I was really relaxed after this crazy week.

Thinking about the consequences of worst scenario if I don’t solved it properly, was all my concerns in that dark time. I will be desperate & disappointed after all these years works independently in scientific researches & suddenly disappear all what you have done.

That’s bad experience  let to consider to put my important files & scientific researches in external disk for secure my works.

Anyway, thanks to The God “Allah” for that day & I hope that other people aware of what happen if you insert corrupted SD card & you don’t have any experience to deal with it. You should use independent PC to fix these kind of corrupted disk/USB Flash/pen drive.

This scientific article was really takes long time to write, collect photo & simulate the new airfoil.

I was extremely exhausted in this 6 months of hard working.

That’s all what we have for today & I will update this article periodically as there alot of works should be finished especially with high Mach number

11) References & Websites:

*References*

Ref-1: Fundamentals of Aerodynamics, 5th Edition by John D. Anderson [PDF]

Ref-2: Airplane design (Aerodynamic), Chapter-5, Wing design – selection of wing parameters, By Prof. E.G. Tulapurkara – Dept. of Aerospace Engg., Indian Institute of Technology, Madras 1. [PDF]

Ref-3: The NACA airfoil series.[PDF]

Ref-4: Principles of Flight, Ch4 – Lift/Drag,(2008). [PDF]

Ref-5: Some High Lift Aerodynamics, Part 1 – Mechanical High Lift Systems, , By W.H. Mason. [PDF]

Ref-6: Advanced Aerodynamic Design Center for Ultra-Efficient Commercial Vehicles, ARMD Strategic Thrust: Ultra-Efficient Commercial Vehicles (Thrust 3A), By Dr. Jim Coder, PI [PDF]

Ref-7: Introduction to Computational Fluid Dynamics, By Instructor: Dmitri Kuzmin, Institute of Applied Mathematics, University of Dortmund. [PDF]

Ref-8: Workshop 04 – Fluid Flow Around the NACA0012 Airfoil, By Dimitrios Sofialidis, Technical Manager, SimTec Ltd. Mechanical Engineer, PhD. [PDF]

Ref-9: ANSYS Fluent Tutorial Guide, Release 15.0, (2013). [PDF]

*Websites*

Web-1: Abbas Ibn Firnas [LINK]

Web-2: The Sky is the Limit: Meet the Engineer Who Tried to Fly [link]

Web 3 : Polymeric Solution for Pump Cavitation [LINK]

Web-4: MIT Engineers demonstrate lighter flexible airplane wing. [LINK]

Web-5: NASA to Test in Flight Folding Spanwise Adaptive Wing to Enhance Aircraft Efficiency. [LINK]

Web-6: CFD model demonstrating the correlation between wall shear stress (WSS) and restenosis in coronary  artery disease [link]