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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186 views

Why is the flow ahead of a shock wave chaotic?

Here is the image of a shock wave on a cone in a small supersonic wind tunnel, the white lines are the condensations formed in the test chamber due to flow expansion. Why are the condensations so ...
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2answers
121 views

How to calculate lift and drag coeffecients for VTOL aircraft in the takeoff stage?

How would I calculate CL and CD for a VTOL aircraft while it is in it's takeoff/landing stage? The particular aircraft is a fixed wing/quadcopter hybrid so I know that I can treat this as a thin ...
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203 views

Why does having a geometry-limited aircraft lead to lower VLOFs?

For this question, please have in mind these excerpts from the 14 CFR 25.107 - Takeoff speeds. "(d) VMU is the calibrated airspeed at and above which the airplane can safely lift off the ground, ...
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127 views

In xflr5,how is the value of Fz calculated?

I am building an conventional plane with AR=6 and I find the wing area,A.So I have selected an airfoil for building my plane that is sd7062. Using xflr5 I got a cl vs alpha graph and I took the cl ...
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2answers
1k views

How do you calculate the lift coefficient of an airfoil at zero angle of attack?

Thin airfoil theory gives $C = C_o + 2\pi\alpha$, where $C_o$ is the lift coefficient at $\alpha = 0$. However, I couldn't find any equation to calculate what $C_o$ is which must be some function of ...
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2answers
245 views

How does an aircraft's weight affect the V-n diagram?

I have a reasonable understanding of what a V-n diagram shows and what the envelope and the boundaries mean. However, the question I have is how does the weight of the aircraft specifically affect the ...
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123 views

How do active blades work on helicopters?

Can someone throw some light on 'active blades' as used in helicopters? I'm mostly interested in the use of piezoelectric material and actuators. How are the actuators able to sense the change of ...
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176 views

Has there been any research on plasma-producing planes?

Many years ago I read in an expository scientific journal[1] an article about what the future of high speed aviation could be. It said that there were studies on airplanes capable of "plasma-izing" ...
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106 views

What is the difference between flutter and vortex induced vibration?

During flutter, the airfoil oscillates with a large amplitude, which generates vortices at the wake. In vortex induced vibration (VIV) the oscillations of the airfoil are caused by the shedding of ...
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1k views

Does the extension of trailing edge flaps increase or decrease the critical angle of attack?

Which graph is the correct representation of the trailing edge flaps' effect on the critical angle of attack? Does their extension increase (as depicted on the first graph) or decrease (as depicted on ...
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294 views

How to properly implement and understand Theodorsen's function?

I'm attempting to implement Theodorsen's lift deficiency function for an airfoil experiencing a harmonic variation in angle of attack due to an oscillating freestream (i.e., not pitch oscillations). ...
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1answer
375 views

What is the constant in this formula for additional lift?

Let’s consider the case of a plane flying s/l in a headwind with a positive gradient. A wing produces lift by inducing a bound vortex superimposed on the relative wind., and in the particular case of ...
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115 views

Why are the boundary layer suction holes placed far forward from the engine?

Edit: I know that the suction holes reduce the boundary layer; I am wondering if there is a reason why they are placed far ahead of the engine’s intake. My thinking is that the long duct past the ...
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1answer
49 views

What are the standard stability derivative formulas and typical GA values?

What are the standard stability derivative formulas and typical GA values? I suppose values for the C172 would be the best benchmark.
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1answer
83 views

How do I calculate the total cruise power from the propelers accounting for the losses?

Let's say I have an aircraft with four propellers (see diagram below) and I am supposed to calculate the cruise power required to drive the aircraft forward. The wing creates the lift and propellers ...
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75 views

What's the theoretical background of the critical angle of attack?

The critical angle of attack seems to be at all (most?) airfoils around 15-20°. Why is that? Why is it in this range and not lower or higher? Is it just the result of optimizing airfoils? Or is it ...
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46 views

Could a moving film of gas reduce aerodynamic drag?

https://en.m.wikipedia.org/wiki/File:Coanda_effect_6.jpg In the image linked there is depicted a system which creates, using the Coandă effect, a film of gas traveling along the surface of a body. If ...
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3answers
251 views

Aerodynamics moment of a wing

An old flight book that I am reading discusses the aerodynamic moment about a wing and talks about an upper and lower lifts. I can see how the pressure distribution on the top surface produces an ...
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204 views

Are there any airplane designs that are (relatively) insensitive to the effects of airframe icing?

Snow and ice buildup on airplanes (especially the wings) is a well-known and feared hazard of cold-weather operations; it roughens the surface of the wings and changes their profile, which combine to ...
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200 views

How to demonstrate that an elliptical circulation distribution can be induced by an elliptical chord distribution?

I intend to demonstrate that a wing with an elliptical chord distribution, without torsion ($\alpha(z)=\alpha=const$) and constant section ($\beta(z)=\beta=const$, and $a_{2D}(z)=a_{2D}=const$), can ...
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220 views

What Inertial effects should be considered to achieve blade stability on a Variable Pitch Propeller tailoredby aerodynamic loads?

I am developing a self adjusting variable pitch propeller tailored by its pitching moments due to aerodynamic loads setting the blade rotation axis in an offset from the aerodynamic center as shown ...
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160 views

Determination of a Joukowski airfoil chord (demonstration)

I'm currently studying Aerodynamics, and one thing that I noticed is that the maximum and minimum $x$ coordinate of the airfoils (which are necessary to compute the chord) on the transformed plane (...
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216 views

Where can I find information on dethermalizer aerodynamics?

A dethermalizer is a device that alters the aerodynamics of an airplane, glider etc, allowing it to descend quickly. Are there any sources - including equations and derivations - on dethermalizers, ...
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825 views

How does corrugated skin influence the effectiveness of ailerons?

Recently I found a paper about incorporating corrugated skins in aircraft called 'Corrugated composite structures for aircraft morphing skin applications' by C. Thill, J.A. Etches, I.P. Bond, K.D. ...
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395 views

What orders of Ram Rise Coefficient (Recovery Factor) are commonly encountered?

The answer to the question about OAT, RAT, TAT, and SAT has the following: Problem is, not all instruments will compress that air in the same way, and not all of them will pick up this Ram Rise ...
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40 views

Do contra-rotating props have worse tip-vortexes than single props?

As I understand it, blades from a propeller have their own tip vortexes, because the blades produce lift under the same aerodynamic principles as wings. So they must have tip vortexes too. So with ...
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1answer
98 views

How is the flow of air through a NACA submerged inlet determined?

This question pertains to the design and/or selection of NACA submerged inlets. I am trying to understand what kind of airflow would enter a NACA submerged inlet/scoop and am looking for a good ...
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38 views

Do open propellers experience pre-entry drag (additive drag) like an engine in nacelle?

Engines in a nacelle experience pre-entry (also called additive) drag. Do unducted propellers experience it too?
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1answer
151 views

Virtual Winglets?

Just read this abstract by a Regeneron STS finalist. Is the idea of a virtual winglet a viable concept? Seems interesting. Link: https://abstracts.societyforscience.org/Home/PrintPdf/15282
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1answer
34 views

Aerodynamic Pressure Loads in FEA of Lifting Surfaces - Query

Let me give a brief summary of the process involved in the FEA of lifting surfaces with the wing as an example: 1. The wing is modelled as a hollow surface body in Ansys, meaning only the exterior ...
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1answer
87 views

What was the decrease in approach speed of the KFIR over the Mirage 5 due to the canards?

The Mirage III approached at 170 knots according to the Dassault. The Mirage NG and the KFIR C2 as well as the Swiss Mirage 5s added canards to the design, what was the decrease in approach speed due ...
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1answer
111 views

Is there a way to calculate the perfect angle of incidence of a horizontal stab for a given airspeed?

I have a Grumman AA1. It’s been modified several times through stc’s to increase power and speed. The aircraft requires full nose down trim to fly level in cruise. Is there a way to calculate the ...
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60 views

Is there a relationship between 2D airfoil aerodynamic results and a revolution body from that airfoil?

The airfoil would be symmetric and the axis of revolution would be its chord line. Edit1: To clarify the question, suppose we have a NACA 0010. Then, using for example XFoil, I'm able to get, for ...
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45 views

Compute Thrust from RPM and Induced Velocity

I'm attempting to calculate the difference in thrust in a secondary propeller operating in the wake behind a primary propeller, in the context of a trailing quad-copter following a leading quad-copter ...
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93 views

What are the effective span and lifting properties of a circular wing?

Today I read an article on FlightGlobal about the Bell air taxi demonstrator. It includes some paraphrased quotes from the Bell VP of innovation, Scott Drennan, among which the following stood out: ...
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48 views

What is the relationship between the Center of Pressure and flap deployment?

I have been reading regarding the Center of Pressure of an airfoil (Cp) and the relationship with angle of attack. What is a good way to explain in layman's terms why the pressure changes in such a ...
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64 views

What is subcritical and supercritical boundary layer?

What is subcritical and supercritical boundary layer? What is the difference between them?
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1answer
101 views

How to determine the thickness of an airfoil?

In calculation or designing, how to determine the airfoil thickness? What is the guideline or consideration in designing airplane's wing? We all know that the bulge (the ticker in the airfoil) is ...
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28 views

How is the inflow velocity distributed of a tilted and trimmed rotor in hover?

I'm wondering of how the inflow velocities per blade look during one revolution of a real-life helicopter in hover (no inflow velocity into the rotor plane) with a tilted rotor plane about 20 deg. Is ...
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105 views

How to calculate the shear centre of a wing?

How is shear centre of a wings calculated? i.e. how can I calculate the wing shear centre of a two spar wing with main spar at 0% of wing chord and rear spar at 75% of wing chord? (Assuming the two ...
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164 views

How to transform a NACA airfoil into a near-circle using the inverse Karman-Trefftz?

Is there anyway to find the leading-edge's center of curvature of a NACA Airfoil? I'm trying to transform a NACA airfoil into a near-circle using the inverse Karman-Trefftz transformation. the ...
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80 views

How much lift can be generated by the intake lip of a duct?

How to calculate the extra lift gained by the intake lip of a duct? Aside from improving efficiency by preventing tip vortices, if a duct has a bell-shaped intake, this lip around the edge creates ...
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122 views

Is this the right way to calculate the roll damping moment coefficient of a projectile in free-flight?

Let's say that I already have data for the spin rate $p\:\frac{rad}{s}$ and velocity of a projectile $V\:\frac {ft}{s}$ in free-flight at multiple points along its trajectory. Presently, I calculate ...
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79 views

What does “lower flatness” mean in airfoil terminology?

What does lower flatness mean in these parameters of a Glenn Martin airfoil?
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387 views

What aircraft has the highest critical Mach number?

What aircraft has the highest critical Mach number? The highest I heard of was BAC/English Electric Lightning at Mach 0.95. Are there planes with higher Mcrit. and is it plausible to go higher than ...
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1answer
172 views

In theory which causes more parasitic drag? A large smooth wing or a small, rough exhaust port?

I'm new to aviation and I have a basic, mechanical question. Wings produce a lot of lift-induced drag, especially at lower speeds. But according to this chart that drops off as velocity increases. ...
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263 views

Why are Leading Edge Flaps (LEFs) create lift while down at slow speeds but decrease lift while down at higher speeds?

When taking off or landing, both LEFs and trailing edge flaps (TEFs) for fighter aircraft are in the down position to provide more lift. However, when flying around at higher speeds (let's say 500-600 ...
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321 views

How do the actuator loads (e.g. for the ailerons) vary between different flight phases?

Assume the hinge moment is given as $HM = 0.5\rho v^2*C_{h\delta} \delta*S*c$ $\rho$ = air density $v$ = air speed $C_{h\delta}$ = Hinge moment coefficient $S$ = Control surface area $c$ = ...
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33 views

How do you design a NACA intake?

What are the construction guidelines to geometrically build a NACA intake (submerged intake) for aircraft. The relationships between the aerodynamic performance parameters (ram recovery, drag, and ...
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39 views

How to calculate the minimum radius of a turn at high alpha, without banking?

How to calculate the minimum radius of a turn at high alpha, without banking? One sees the radio control guys flying their planes at 30deg AOA in a 5' circle at walking speed, without banking. ...