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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1answer
97 views

Why do fixed slats have a cusp?

Reading this about slat cove filler meant to reduce aeroacoustic noise, it seems there is no big difference in lift if the cove filler is deployed or not. I understand the shape of a retractable slat ...
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3answers
287 views

When pitching, how do planes establish a pitch rate which corresponds to the centripetal acceleration?

Coordinated flight requires that the yaw rate and the centripetal acceleration correspond. In other words, for a given $a_{centripetal} = v^2/r = \omega ^2 r$ this means that the yaw rate must equal $\...
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1answer
58 views

What are the effects of increasing Wing Aspect Ratio?

I can think of only 2 effects that is The Induced Dag would Reduce with increasing AR of wing. This goes by the simple formula: $$ C_{d(i)} = \frac{K \times C_l^2}{\pi \times \text{AR}} $$ As drag ...
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1answer
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Charger vs Bronco horizontal stabilizer volume?

While watching this video on the Convair Model 48 Charger, I was surprised by the dimensions of the horizontal stabilizer. Compared to the North American OV-10 Bronco, which is relatively similar in ...
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1answer
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What is the maximum control surfaces deflection on a Cessna 210N?

Does someone know how far the control surfaces (rudder, ailerons, elevator and nose gear) can deflect in a Cessna 210N? I've been searching Google and the POH for hours now and can't find it.
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1answer
82 views

How does the stick force and behaviour of aircraft relate to the CG locations?

I'm struggling with developing an intuition for flight behaviour and stick force with CG locations. Assuming conventional wing and tail configuration, When the CG is moved from aft to forward, the ...
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59 views

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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1answer
233 views

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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1answer
98 views

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. ...
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1answer
75 views

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 ...
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42 views

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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1answer
40 views

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 ...
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2answers
215 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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42 views

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 ...
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1answer
279 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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1answer
85 views

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 ...
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1answer
400 views

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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3answers
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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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1answer
118 views

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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1answer
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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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2answers
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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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106 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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1answer
532 views

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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27 views

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,...
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1answer
61 views

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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1answer
2k views

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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5answers
677 views

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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1answer
83 views

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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57 views

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 ...
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56 views

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?
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88 views

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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3answers
170 views

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 ...
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3answers
167 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 ...
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2answers
123 views

Does anyone know why IAS and Mach are inconsistent in Boeing FCOM?

The following figure is extracted from Boeing FCOM that I downloaded from the Internet: I noticed that Mach and KIAS values are inconsistent. An example is in red box. Let me show what I found: $$ \...
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3answers
203 views

How can I make a serious wind tunnel?

I am looking for specifics of building and the operation of low speed wind tunnels, but most diy wind tunnels on internet are improved versions of science fair projects at best. What would I need to ...
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1answer
112 views

What causes air flow towards fuselage near the winglet?

I am trying to understand how winglets are beneficial in reducing induced drag and I came across this article; https://www.boldmethod.com/learn-to-fly/aerodynamics/how-winglets-work-to-reduce-drag-and-...
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1answer
63 views

How does the position of Maximum camber affect lift and drag on an airfoil?

I am trying to understand how varying the maximum camber position of an airfoil will affect the lift and drag it generates. For instance considering NACA 2415 having maximum camber at 40% of cord ...
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3answers
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Projected Area & AoA - Projected area of the wing is variable (as projected on to a surface that is perpendicular to the relative wind)

Does Wing Area vary with angle ot attack? Edit: why we don't recognize that the projected area of the wing as variable (as projected on to a surface that is perpendicular to the relative wind) Per the ...
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How can I calculate the pressure coefficient and stagnation temperature?

How would we find the critical pressure and stagnation temperature if we are given the Mach number, density, freestream temperature and the pressure on a point along the wing?
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Distance where transition from laminar to turbulent boundary takes place

How do we work out where the distance from the leading edge the laminar boundary layer would turn into a turbulent boundary layer? Assuming we have been given the length of the plate, speed, dynamic ...
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2answers
103 views

How can I calculate the tail area required to achieve longitudinal static stability?

I've got a longitudinal stability question. I've not attempted this question yet as I didn't know where to start from, also my lecturer hasn't explained static stability to us clearly and I needed a ...
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1answer
99 views

How do you quantify rudder effectiveness as a function of bank angle?

I'm currently reviewing just for fun aircraft dynamics based on OEI (one engine inoperative) scenarios. After reading that "lower pedal forces at higher bank angles" are required, it got me ...
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4answers
199 views

Hypersonic Boost Glide Range

Looking at an article earlier about hypersonic boost glide vehicles and I noticed how small their L/D ratios were ~2.5/1. If they begin their hypersonic glide at 50km in altitude would they not ...
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What is the physical explanation for the pre-stall judder in a Spitfire?

From the book "First Light" by Geoffrey Wellum, where the author describes dog-fight manoeuvres against an Me 109: If you want to shake someone off your tail you have to fly your Spitfire ...

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