# Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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### Is the Centre of Gravity moved by an aircraft travelling at “High Speeds”?

The following quote is from G. Bristol’s book, Ace the Technical Piloting Interview: [The] movement of the centre of gravity is due to a change in weight. The distribution of the aircraft’s weight ...
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### Aspect ratio of an elliptical wing

I am looking into elliptical wings at various aspect ratios and my intuition tells me that an elliptical wing with aspect ratio of one is a circle, meaning the chord and the span will be equal. But, ...
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### Are there retractable, compact hang gliders?

I was wondering if there were hang gliders that you could, say wear on your back, in which the wings would retract into the suit. Kind of like the falcon in the mcu? If they aren't there, why not?
253 views

### What is the indicated airspeed necessary to exit ground effect on takeoff?

I always thought that a plane needed to be at stall speed or greater to be able to exit ground effect on takeoff. However, after seeing the YouTube video in the link below I am not so sure. ...
244 views

### Reference area in lift coefficient calculation

Does the reference area changes with angle of attack? Most sources says it is projected area. If it is projected area then it should depend on Angle of attack. I want to calculate Lift and drag ...
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### By aircraft design, excluding engine power, how do you make planes that have a tight turn radius while maintaining speed?

What are all factors in design, excluding engine power and acceleration, thrust vectoring and flight computers, that makes a plane that have a real tight turning radius while maintaining speed? Like ...
132 views

### In terms of aerodynamics, what is a polar?

Many aerodynamics discussions (including several on this site) talk about "polars" without ever explaining what they actually are. As with any technical term common to a field, once the ...
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### Maneuvering Speed Discrepancy

In this page from the limitations section of the Extra Flugzeugbau 330SC, it states I’m curious as to the discrepancy between maneuvering speeds Va between operation in the Normal Category and the ...
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1 vote
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### Could the center of pressure be not on an aircraft?

I have created the outer mold line of a blended wing body drone and have put it through Ansys Fluent. Using SST k-omega turbulence model and 40 m/s of airspeed. However, the output from the program ...
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### How does the velocity of a turboprop engine relative to the airplane change when a plane is banking?

I saw this YouTube video recently: And in it, a turboprop engine propeller and gearbox comes out and slashes across the underbelly of the plane, crippling the aircraft....
1 vote
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### Why does power go up with the cube of the airspeed?

If i have an airplane with over 100 kN of thrust, and i want to accelerate from a velocity at which drag force is 25kN to a velocity twice higher, is it possible that i wont be able to do this because ...
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### What's the relationship between mach number and drag force on an airplane?

From what i've read drag coefficient at mach 1 is several times (up to 10x) the drag coefficient below drag divergence mach number. It drops as the mach number increases. It's easy to find plots ...
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### How do you maximize lift while keeping span as short as possible?

This weekend I saw the Fly Baby at the Smithsonian Air & Space Museum at the Washington Dulles Airport, and it was at some point the smallest airplane (since surpassed by the Bumble Bee II, if I ...
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### What is the difference between Vs and Vs1g?

As the name suggests, what is the difference between Vs1g and Vs? If both of them are referring to the stall condition, why they aren't the same? Which one is usually greater and why? Why do we need a ...
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### If Navier-Stokes equations are unsolvable how does CFD software calculate simulation? [closed]

Navier-Stokes equations are one of the problems of the millennium. How, then, are CFD programs doing simulation, calculating forces, etc if these equations are unsolvable?
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### Why does lift decrease and drag increase when approaching the stall condition?

This is an ECQB-PPL question specifically asking what happens before the stall. I do understand that after the critical angle has been reached, the airfoil is no longer generating lift (so obviously ...
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### Can a jet-engine aircraft fly all the way to its service ceiling at its maximum takeoff weight? [closed]

I am trying to understand how high an aircraft can get to at its maximum takeoff weight (minus whatever fuel is consumed in getting to that altitude). Can it make it all the way to its service ceiling?...
1 vote
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### Is aerodynamics science still being discoverd? [closed]

Is aerodynamics science still being discovered(like mathematics for example) or everything has already done?
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### Why is the ball no longer centred in a multi-engine airplane with inoperable engine?

I'm currently working on my PPL, and whilst trying to understand fully how the turn coordinator works, I got down a rabbit hole that makes me question my understanding, and that I can't dig myself out ...
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### Why do smaller RC helicopters have visible twist in their rotors, and slightly bigger ones do not?

Smaller, cheap, RC helicopters generally have very pronounced twist in their blades, and also vary their chord - slightly larger, slightly more expensive RC helicopters have no visible twist or chord ...
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### Would blade-less (Dyson style) jet engines work? [duplicate]

Is it possible to design an aircraft with blade-less (same concept as Dyson) design to generate thrust? What are some of the key benefits, drawbacks and examples of attempts (if any) at this kind of ...
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### What causes ram air turbines with more blades to spin slower than turbines with two blades? [closed]

Lets say aircraft has two ram air turbines that work as generators to produce electricity on each wing. One has two blades and one has 8 blades, both with the same diameter. What is the aerodynamic ...
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1 vote
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### What is the difference between buffeting and wake galloping?

I am interested in flow-induced vibration and confused between buffeting and wake galloping. As far as I have studied, both phenomena are the vibration of an object with another object in front of it. ...
1 vote
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### Does closed oval wing produce two vortex and downwash between them, like normal wing? [duplicate]

Does closed oval wing like this in video produce two vortex and air between them goes in downward direction like on normal wing? I think yes ,because cause for downwash is wing that push air down, not ...
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### How does the downwash change the effective AoA if it happens behind the wing? [duplicate]

In this video (biologists.com) I see two vortices and the air between them goes in the downward direction; that's supposed to be the downwash. But the downwash (induced vertical airflow velocity) ...
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### Can a fixed pitch propeller be designed to act as both a propeller and a generator?

The angle of attack (AoA) plays a major role in designing a propeller for specific uses, such as if it is to be designed for aircraft propulsion the AoA must be high, while the AoA must be low if it ...
134 views

### Does tailless delta configuration retain any advantage over conventional configuration with straight wings at high subsonic speeds?

For a model aircraft designed for cruise at say 0.75 Mach, do delta wings offer any benefit over straight wings. Is drag saving from elimination of the tail large enough to consider a delta ...
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### What is the reason that the Russian flying wing UCAV does not have sharp leading edges?

The new Russian UCAV sports a fairly blunt leading edge while all the other UAVs in the same category have sharp leading edges.
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### What means when center of pressure is out of physical dimension of wing?

Center of pressure(CoP) is point where total force vector acting at. If you hold wing at this point, wing will not rotate(moment=0). Example hanging point at hanglider. I see at some diagrams for very ...
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### How the AOA, Pitch and FPA are changing during a flight maneuver

For a steady state flight, there is a equation that FPA + AOA = Pitch, but how these three variables are correlated during a flight maneuver like currently I am in a leveling flight and then I want to ...
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### Why the European Eurofighter Typhoon did not have pitot tube in front of the radome? [closed]

The layout of the aircraft does not have the proper pitot tube. I believe that the aircraft needs clean airflow for its instruments .
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Some days ago I saw the accident of the airtractor that, just after a drop, suffered a spar failure in both the wings. Luckily the pilot survived. If load factor in his simplest formula is: n=lift/...
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### How calculate lift/drag using static pressure taps in wind tunnel test?

An airfoil section in a wind tunnel has many static taps on its upper and lower surface. These static ports can only read static pressure which acts perpendicularly to the local airfoil surface. In ...
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### Help with calculate forces from pressure distribution

V=50m/s deltaPg= -981 Pa deltaPd=490,5 Pa c=1m r.com/PCshZ.png Above is calculate Fz with integrals and with average pressure. Why F3 is calculate from 0 to C/2 if pressure distribution is drawn at ...
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### Why did Concorde have a large anhedral?

Why does Concorde and many other deltas have their wings bent down?
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### How to solve normal and axial aerodynamic force coefficients integral equation to calculate lift coefficient for an airfoil?

$$c_n = \frac{1}{c} \left[ \int_0^c (C_{p,l} - C_{p,u}) \, dx + \int_0^c \left(c_{f, u} \frac{dy_u}{dx} + c_{f,l} \frac{dy_l}{dx} \right) dx \right]$$  c_a = \frac{1}{c} \left[ \int_0^c \left(C_{p,...
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### How would you design an airplane to counteract a single engine’s left turning tendencies?

How would you design an airplane to counteract a single engine’s left turning tendencies caused by torque, p-factor, spiraling slipstream and gyroscopic precession without pilot input or use of rudder?...
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### Airflow through axial flow compressor

So I'm reading the Gas Turbine Engine Fundamental, and suddenly come across the airflow passes through one axial compressor stage. I wonder why the Resultant Rotor Inlet Velocity is pointing downward,...
278 views

### Why don't competition gliders use riblet skin surface to reduce drag?

Price is not a problem in competition gliders, also no problem with in maintenance surfaces like at airliners. It is very easy to wash glider before every race. A riblet surface is proven (PDF) to ...
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1 vote
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### Will wing rough surface shift flow separation upstream?

A rough surface takes energy from the boundary layer, so doesn't a slow, "tired" and thick boundary layer have too little momentum to fight against an adverse pressure gradient? If the wing ...
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### How to calculate lift coefficient using pressure distribution?

Above is the image of the question I want to ask. Please clarify on how the pressure coefficients of the upper and lower surfaces of an airfoil can be used, also if there is a set equation to ...
138 views

### Once pressure distribution is established, why soft wing at zero AoA without battens can't maintain shape?

Imagine we have soft wing with curved battens installed in wind tunnel set at zero AoA.Wing has camber,so it produce lift. If we remove battens from wing during wind tunnel test when wing produce lift,...
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### Can a wing be stalled at a speed larger than its stall speed?

I was told pulling the yoke quickly and all the way back stalls the plane immediately. I believe this is not possible as long as this occurs above the stall speed. I think about a styrofoam plane: ...
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### Will computational fluid dynamics (CFD) ever be 100% correct?

CFD results never match real world numbers especially in turbulent 3D complex flow... What stops CFD being perfect, and will it ever be 100% correct? If the Navier-Stokes Millennium problem is solved, ...
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### How does the flight controls performance differ in a compressible and in compressible environment?

I know that in low speed flight compressibility effect is negligible and in high speed there will be an effect but how do they differ in flight controls such as primary and secondary?
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### Why does the centrifugal twisting force move variable pitch propellers to fine?

In my research on the forces acting on and influencing a single engine, non feathering variable pitch propeller's ability to change blade angle, I've come across a bit of a roadblock. Aerodynamic ...
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### On which point are the moment coefficients of the NACA airfoils measured? [duplicate]

On airfoiltools.com website, for example: NACA 2412, they give airfoil data. One of it is the moment coefficient of the airfoil vs the angle of attack of the airfoil. However, these moment data could ...
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### Derivation of the axial force coefficient for an airfoil in terms of the pressure and skin friction coefficients

In chapter 1.5 of Fundamentals of Aerodynamics by Anderson, there is an expression for the axial force coefficient of an airfoil in terms of the pressure and skin friction coefficients. However, "...
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### Is the fuselage of the CEA 311 Anequim configured as elliptical?

I am currently studying the effects of reduced drag induced by laminar flow on the subsonic aircraft. In order to complete that, I have believed I found the optimal fuselage which has the best ...
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### How does the wake behind a propeller blade affect the next blade if the airflow through the propeller should be clearing the wake?

Propeller or wind turbine often has only 3 blades,reason is wake behind each blade interfere with next blade. I think wind that comes to propeller must clear this wake,so faster you go the air for ...
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