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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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Can be the divergence Mach be greater than 1?

I am wondering if this is possible. I know that by decreasing t/c and increasing the sweep angle it is possible to increase the divergence Mach. Where is the limit? I am calculating the Mach for a ...
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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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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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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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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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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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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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Air flow over an airfoil

We know that in real viscous flow, boundary layer exists around the airfoil and there will be a separation point which flow starts to separate from the back of the airfoil( velocity gradient equal ...
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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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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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166 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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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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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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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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How to calculate the power required during transition from VTOL to fixed wing?

In a VTOL, I have calculated the power required for take off and cruise which was not difficult at all. Between take off and cruise, there is a phase where the VTOL has to transition by tilting the ...
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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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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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Are there any aircraft designs that are (relatively) insensitive to the effects of airframe icing?

Snow and ice buildup on aircraft (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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Does the Lilium VTOL wings produces lift during takeoff?

I just had a look on some of the recent development in the personal VTOL electrical aircrafts. I am wondering if the Lilium VTOL wings produces lift during takeoff? I would expect a quit high wind ...
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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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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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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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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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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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What is formula for induced drag in stalling regime?

I'm wondering what is the formula for induced drag in a stalled regime, i.e. in a regime where the $C_L$ (coef. of. lift) has started to decrease but is still nonzero. I've a feeling that the ...
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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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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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Why do the elliptical and the rectangular wing show different aerodynamic efficiency?

I understand the elliptical planform is aerodynamically the most efficient type of wing planform and generates the greatest L/Dmax, but it's difficult for me to understand why. What makes the ...
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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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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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364 views

How is Reynolds Number derived and used?

Reynolds number is the ratio between inertial forces and viscous forces according to wikipedia. However, I still do not understand its derivation process and how to, for example, calculate the ...
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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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What is subcritical and supercritical boundary layer?

What is subcritical and supercritical boundary layer? What is the difference between them?
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What is the glide ratio on the CE-S550 Citation S-II?

I couldn't find it in the AFM. Is it different then the square winged citation II?
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Where am I wrong at aerodynamic center calculation?

I'm currently taking aerodynmics course.In the classical thin airfoil theory. we saw that both for symmetric and non-symmetric airfoils the term $dc_l/d\alpha= 2\pi$. But in the preceding chapter, ...
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How do split winglets reduce bending moment in the wings?

I am doing a study on split winglets and how they are more advantageous than blended winglets . While browsing through the net, I was reading an article about the Boeing 787 Dreamliner and they had ...
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Determine “basic lift distribution” over a wing that has a circulation distribution

I don't understand what they mean with basic lift distribution. I have calculated C_L which is 5a (a is alpha in radians). I added the relevant equations here.
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Is winglet height equivalent to duct height?

Winglets increase effective wingspan by causing vorticies to be generated further away from the wing root in proportion to the height of the winglet (if vertical), likewise with winglets on propellers....
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What are stick position stability and stick force stability?

What are stick position stability and stick force stability? What are the difference between them? How will changing trim of an aircraft affect them?
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what is the impingement location of Streamwise vortices?

When I was reading an article about scalloped and lobed mixers in turbofan engines nozzle, I faced with this sentence that was comparing lobed and scalloped cases: "impingement location for the ...
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What would the consequence of placing the data probe beneath rather than free of the boundary layer be?

In NASA report TP-2005-213766, a study on s-ducts and boundary layer ingestion, a paragraph in the observed results admits that the predicted boundary layer was too small, in fact being a thickness of ...
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Propeller air displacement

I was thinking about propeller design just now and it came to mind that, theoretically, the air displaced by the propeller after every rotation might not be able to "flow back" into the area "served" ...
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How can I find or calculate typical flutter velocities for different wings?

I need to validate a code I wrote for calculation of dynamic aeroelastic response of a wing for my aeronautical engineering Master thesis. I'd like to ask if anyone may provide me a list with typical ...
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How does a mixer reduce noise in a turbofan engine?

I want to know how does a mixer reduce noise in a turbofan engine? How does its shape influence the flow and the acoustics of the output air generally?
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How can I calculate the lift force on an aircraft pulling out of a dive?

Any ideas on how this question is answered? Consider an aircraft dived [sic] along a path inclined to horizontal, perhaps even a vertical path. The manoeuvre whereby the aircraft recovers from ...
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298 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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If elliptical lift distribution is considered in every case, does the induced velocity change based on the shape of the wing?

Shapes like rectangular, curved, trapezoidal etc. Here I mean rectangular or curved when viewed from the top. The sectional airfoil shape is the same in each case.
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Is there a fixed ratio between highest L/D and max endurance L/D?

It can be demonstrated that, for any airplane, there is a fixed ratio between the maximum range and maximum endurance speeds (1.31607...). Does another, fixed ratio exist between highest L/D and L/D ...
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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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Can a large aspect ratio wing be actively controlled using distributed electric propulsion to avoid getting ripped apart in wind shear?

This question is related to the recent possibility of solar aircraft becoming flyable. Solar Impulse, the NASA Helios, and the Titan Aerospace/Ascenta Aerospace solar drones have all have issues with ...