# 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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### How to calculate how much horsepower is needed to negate wing tip vortices with a wing tip prop?

How to calculate how much horsepower is needed to negate wing tip vortices with a wing tip prop? I understand 80% of drag is at the wing tips. Source: Xflaero software notes. I understand NASA's X-57 ...
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### Is NASA's X-57 using a fan, a prop, or a prop/fan and what is the difference visually/physically?

Is the NASA's X-57 or the Opener BlackFly using a fan, a prop, or a prop/fan and what is the difference visually/physically? NASA X-57 Maxwell, courtesy of Wikipedia Opener BlackFly v3 courtesy of the ...
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1 vote
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### Do aircraft usually fly with CG at 50 percent of chord or do I need to reduce the tail volume?

I'm working on a design having a 3.2-metre wing with a constant chord section in the middle and taper on the sides. With a tail volume of about 0.68, the neutral point is at 60% chord from the leading ...
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### Why aren't takeoff flaps used all the way up to cruise altitude?

In general aviation aircraft such as Diamond star DA-40, flaps to take-off are used until 500ft AGL and speed before retracting flaps is Vy (best ROC speed)-67kts and after retracting flaps is 80kts. ...
1 vote
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### I have a projectile going through the air, point in front, flat plate in the rear. How do I calculate the aerodymanic forces on the rear plate? [closed]

The project that the projectile is being developed for has nothing to do with aerodynamics, but the problem is that the rear plate is being sucked off - obviously not attached sufficiently. How can I ...
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### I don't quite understand the derivative in this vertical wind gust formula

First my english writing skill is still bad so pardon me if i accidentally made any mistake TT-TT. So recently I have learnt about how the vertical gust affect the load factor and the calculation ...
1 vote
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### Variables of Dryden Wind Model

How to determine the turbulence intensities (σu, σv, σw), scale lengths (Lu, Lv, Lw) & Angular frequency (ω0) in the given Dryden wind model to generate wind speeds (u_w, v_w, w_w) of civil jet ...
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### Does the Prandtl-Glauert correction use the airplane's Mach number, or its effective Mach number corrected for sweep?

The Prandtl-Glauert correction adjusts the lift curve slope of an airfoil to different Mach numbers. Should the Mach number of the airplane be used or the effective Mach number that the leading edge ...
288 views

### Will air accelerate over a wing and generate lift, if the air has zero viscosity? [duplicate]

Will air accelerate over a wing, if the air has zero viscosity? Will the wing produce any lift under these conditions?
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### Streamline Curvature Theorem applied to Airfoils?

I am new to studying aerodynamics and taking up aeromodelling and am currently learning how lift is obtained in-depth. When studying the two common explanations as to how lift is generated by an ...
465 views

### Is all the extra lift from flaps added upstream where the spars sit?

Flaps can significantly increase the lift for a wing, is all that extra lift added upstream where the spars sit? I ask this question because the flaps in airliners seem to be only connected by a few ...
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### How would you adjust C_l airfoil values for different Reynolds numbers?

I have graph of C_l (airfoil lift coefficient) as a function of AoA, for Mach 0.7 and Re = 6x10^6. For a given value of C_l, what would be a good way to estimate that value at a different Reynolds ...
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### How do thick and thin airfoils compare in lift generation?

I find myself confused when comparing the lift generation amongst Thick and Thin Airfoils. A paper to which I have added reference below claims that thin airfoils are better in generating lift because ...
1 vote
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### With 77% less wing area than the Lazair Ultralight, how does the Blackfly meet FAA ultralight category requirement of power off stall speed of 28mph?

With 77% less wing area, how does the Opener BlackFly do a power off stall at less than 28mph (or fly with no power at 28mph)? I understand the Lazair with 140 sq ft of wing area, was able to fly at ...
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### Is the compressor required on jet engines? Can air be rammed into the turbine?

In the context of a common airliner (say Boeing 777), when the airplane is on the ground, and the turbines are on, air is getting sucked in and compressed/bypassed. The engine has to do work to ...
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### Are shrouds and stators needed to maximize thrust from stacked props and motors in electric aircraft like the Lilium Jet?

Do some e-vtol aircraft, like the Lilium need shrouds and stators to maximize thrust from stacked electric motors and props? The aircraft is actually called the Lilium Jet, although it does not heat ...
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### Why do low pressure arrows point away from the surface if the pressure/air cannot pull/suck?

Pressure is always positive, so at the upper part of a wing pressure is positive as well, just lower than the free stream, but still PUSHes on wing surface, not PULLs. Words like pull or suction don't ...
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### Is there a name for the fast decline + pull to climb pattern?

I'm a hobby photographer and I've noticed some patterns in the bird flights, so I tried to poke a bit into the aviation terminology for it. Phalacrocorax carbo does this movement similar to the ...
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### Do all Fuselage sections have same performances?

The Burnelli machines had an airfoil shaped fuselage; some indicate near 10% of lift in a 21 century airliner comes from fuselage; 'Flying Wing' concept is old, and still attracts many; bottom of ...
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1 vote
143 views

### What are the relations between Angle of attack and Calibrated Airspeed?

I would like to estimate Angle of Attack using trigonometric relations i.e AoA = arctan (w/u) airspeed components (i.e u, v, w). When I am considering body 'x' velocity ('u' component), is it ...
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### Why are there two local maximums on some CL vs AOA curves?

I know what a stall is but I don't understand why there are in some cases two local maximums on the $C_L$ vs AOA curve of some airfoils. What is the reason for the mini stall that occurs before the ...
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### Does form drag require skin drag?

Theoretically, if there was sphere with zero skin drag, would that make form drag nonexistent? If fluid could flow around symetric object whose shape doesnt generate any lift without any skin friction,...
1 vote
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### Does the quarter-chord-angle rule still hold for wings with very long chords or large differences between leading- and trailing-edge sweep angles?

For most fixed-wing aircraft, the effective wing-sweep angle (i.e., the angle that the aircraft aerodynamically behaves like its wings are swept at) is equal to the angle of the quarter-chord line (...
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### What is a laminar airfoil and what are their pros and cons?

I am wondering what is a laminar airfoil and what are their advantages and disadvantages if compared to other designs.
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### Which way does the F-16 cannon rotate, and why in that direction?

The F16 cannon is turning when fire the bullets. What is the direction when looking from the front of the aircraft towards behind?
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### Why do the B-2 Spirit's split elevons seem almost always deployed?

Looking at images and videos displaying B-2 spirit, it seems like split elevons are most of the time deployed, even at high speed. Why is it so? Having some aerodynamic surface deployed generates drag ...
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### What is the principle behind flight of airplanes? [duplicate]

What is the principle behind flight of airplanes? Need a simple answer for grade 7 student. Thank you
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### How are shear winds studied experimentally?

I've played extensively with wind shear Math models, but I wonder how the aerospace researchers study it experimentally: Do they generate shear flows in a water tunnel? Or do they use a wind tunnel? ...
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### Circulation around an airfoil at negative α

I was recently reading this very helpful string What is the physical meaning of circulation found in Kutta condition? and it explained very nicely potential flow around an airfoil. My question then is ...
1 vote
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### How are panel codes like xfoil able to model turbulence and predict drag?

Since Xfoil is using potential flow theory, how is it able to predict boundary layer and separation? If I'm adding perturbation terms aren't those still made with fundamental flows?
1 vote
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### What do these terms related to airfoils mean?

I keep coming across some terms related to airfoils and I'm not able to find clear definitions for these terms. Bubble ramps pressure recovery suction side
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### Why should Mach wave angle be less than wing sweep angle?

This is from my lecture notes: I see that this is so you can have subsonic flow over the wing planform, but why is this desirable? And are there more reasons? I can think of heat being an issue if ...
346 views

### Ground effect and Lift coefficient

Is there a correlation between the lift coefficient and the proximity between the wing and the ground? I know that the lift coefficient is dependent on angle of attack; However, based on experiments ...
158 views