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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22
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3answers
4k views

Do aircraft at cruise bob and/or skip?

Recently I started flying a model aircraft, admittedly a kindness for a motor stuck onto a piece of foam, and have noticed that it either bobs, for lack of a better term, like something afloat on ...
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1answer
191 views

What would happen if a hot air ballooon was punctured in mid-air?

I am writing a script for a film where a hot air balloon is punctured and it falls to the ground. There are two teenagers in the balloon when it is in the air. What I would like to know is how fast ...
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1answer
108 views

Why is CL/Cd equal to L/d?

I'm making a school project where I intend to design and calculate an rc airplane. Reading some books I found something I can't understand, it says that CL/Cd is equal to L/d, but the only possible ...
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1answer
92 views

Does flutter disappear above the flutter speed?

Okay, lets assume we have an airplane with some sort of superstrong wing, but otherwise conventional configuration. We accelerate it gradually. Eventually, it will reach flutter speed, at which the ...
2
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2answers
217 views

What are the forces present in a coordinated turn?

During straight and level flight, coordinated flight is assumed when there is no net lateral force (no slip or no skid). But this concept totally breaks down when it comes to turning, in a co-...
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4answers
191 views

Why are true and indicated airspeed different?

So, I understand that True air speed is the motion of aircraft relative to air around it. And, indicated airspeed is speed arising due to dynamic pressure. Considering a true airspeed of 100 knots, ...
2
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1answer
89 views

Would plain and slotted flaps increase lift substantially in a distributed propulsion application?

Would plain and slotted flaps increase lift substantially in a distributed propulsion application for a slow moving aircraft (15mph)? I understand that: A classic NACA foil without flaps such as the ...
2
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3answers
223 views

Why is air accelerating over the wing surface?

I know that there are dozens of questions about lift generation here but after reading them I still don't understand everything. My question is: why does air accelerate over the (upper side) wing? I ...
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1answer
44 views

How do you calculate the wing moment coefficient knowing the moment at each spanwise station?

A lot of theoretical formulas exist for finding the moment coefficient for airfoils, but I have been confused by how to get the moments for a wing. I came up with three related questions that have ...
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0answers
112 views

How can a designer deal with a strict requirement when designing an aircraft?

I'm working on designing an aircraft with some specific requirements (Vstall, Vmax, Ceiling, Payload, Range, RoC, Slanding/takeoff etc). I'm following Anderson's and Raymer's ways (trying to find the ...
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0answers
23 views

The lift and moment of the tail equations

We have The lift of the tail, $$ L_t = C_L.q.S_t $$ The moment of the tail around c.g. $$ M_(cg,t) = C_M.q.S.c $$ look at the S in the two equations. Why the lift of the tail is proportional to the ...
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2answers
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In the context of aircraft design, what are the differences between a flat plate shaped airfoil and a droplet shaped airfoil? [closed]

I am relatively new to aerodynamics and am curious to know what difference it makes on an aircraft - lift, drag, weight etc - which of the two airfoils is used on the wing.
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1answer
112 views

What is the angle of Incidence of wing of Airbus A320?

What is the Angle of Incidence/ Mounting Angle of the wing of AIRBUS A320?
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3answers
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Thrust is going towards the earth, but the plane is going upwards, Why? [closed]

Dears, I am trying to develop a flight simulation, but I am facing a problem when the plane goes downwards towards the earth. As shown in the picture below: In equilibrium state before the plane ...
1
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1answer
96 views

How does vorticity change the lift coefficient of an airfoil?

For airfoils in unsteady motion, the lift coefficient oscillates and the wake is characterized by vortex shedding. How does vortex shedding affect the lift coefficient for an airfoil?
3
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1answer
200 views

Is it possible for Mig 21 at corner speed to extend the flaps to minimize the turn radius? Or this is not an option?

The corner speed is around 330knots if you want to turn better than the enemy is possible to lower the flaps?
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1answer
97 views

Did the Mig 21 have differential stabilators to help the ailerons?

The MiG 21 had all-moving tailplanes or stabilators. When rolling, did one stabilator pitch up and the other down to act as secondary ailerons and help the main ones on the wing?
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2answers
135 views

Helicopter retreating blade stall: Increasing the fwd speed decreases the tip speed on retreating side and angle of attack. So why limit on V_n.e?

On Retreating side: Speed of wind over blade tip = blade rotation speed - forward speed. So, with an increase in forward speed, the speed of the wind over tip is getting reduced. In airflow diagram, ...
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0answers
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Why are the wingtips of the Fairchild-Republic A-10 bent downward? [duplicate]

Why are the wingtips of the Fairchild-Republic A-10 bent downwards?It is subsonic aircraft .
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3answers
1k views

What is the difference between flow separation and turbulent flow?

For air flowing over a wing, both flow separation and turbulent flow involve disturbed flow next to the surface and smooth flow further away. At what point does one say "oh, this flow has changed ...
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1answer
83 views

How to use a set of Pressure Transducer to mimic pitot static tube for VTOL vertical airspeed indicator?

May i know if i have 3 pressure transducer, 1 facing upwards and the other downwards to measure the vertical velocity of a VTOL (Vertical Takeoff and Landing aircraft) and another 1 on the nose of the ...
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0answers
58 views

Is it true that blowing cannot be used for laminar flow control? Why?

Aerospace Engineering Desk Reference, page 505 Tangential blowing can only be applied to the prevention of separation...The flow caused by blowing tends to be very vulnerable to laminarturbulent ...
2
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3answers
109 views

Is there any non-experimental way to obtain CL, CD, and CM as a function of the angle of attack and the control surface deflection angle?

I am working on a flight simulator for control algorithm testing. The issue I am facing is to come up with a relationship between CL/CD/CM and the angle of attack ($\alpha$) and the control surface ...
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3answers
225 views

Why do the two different “ground effect”s used by aircraft and automobiles do opposite things in almost the same conditions?

I found How come the ground effect has such a different outcome for wings and cars? and: I am not allowed to comment as a new user because of some weird rule and I do not know enough to answer the ...
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1answer
68 views

Will a quad fan arrangement on an aircraft help with pitching moments during VTOL flight transition?

The phenomena of ducted fan assemblies inducing pitching moments whilst in transition from vertical to horizontal flight paths is a problem I have seen mentioned by many designers and engineers of ...
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1answer
30 views

Can the wing stagnation point be bled off and used for laminar flow control?

The stagnation point at the leading edge contains slow-moving, slightly compressed air. This sounds ideal for laminar flow control. This slow air will create little losses in ducts, and it's pressure ...
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2answers
102 views

Do biplanes need bigger tail volume coefficients than monoplanes?

Do biplane ultralights need bigger tail volume coefficients than monoplane ultralights? Horizontal Tail Volume Coefficient I understand that biplanes don't need a larger horizontal tail coefficients ...
2
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1answer
92 views

Does an airfoil in supersonic flow have zero circulation?

In incompressible flow, the Kutta-Joukowski theorem can be used to relate the lift (per unit span) to the circulation around an airfoil. However, if we look at an airfoil or the flat plate (see below) ...
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1answer
74 views

How do the vortex created by wing tips affects the lift? [duplicate]

I’ve been reading about how improve the aircraft performance and I found that for low aspect ratios, the vortex created by the wing tips decrease the lift generated by the wings. Why is this happening?...
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1answer
52 views

Does thin airfoil theory work at very high angles of attack?

Thin airfoil theory says that lift coefficient is directly proportional to the angle of attack in radians. I haven't been able to find any limit, short of stall, for applying this theory. It would ...
3
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2answers
112 views

What are the forces acting on an air particle along curved streamline(wing upper surface)? [closed]

What forces act at air particle at curved streamline (at first 1/4 upper wing surface) , looking from inertial and non-inertial frame of reference? (show free body diagram) Pressure gradient normal ...
3
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0answers
113 views

why are the Comet's engines pointing outwards?

As it's visible from the images below, when looking at the plane from the top, the engines point outwards and they are banana-shaped, why is that? (unfortunately I couldn't find a real photo ...
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1answer
118 views

Why does spoiler extension during touchdown causes a pitch up moment?

There are reports that incorrect flight technique associated with spoilers extension during touchdown were contributing factors to pitch increase after landing, causing tail strikes in jet transport ...
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1answer
97 views

Why does pitching moment coefficient decrease with an increase in the angle of attack?

Slope of Cm vs alpha graph is negative, why it is so? The attached graph is from https://en.m.wikipedia.org/wiki/Pitching_moment , this graph is for cambered airfoil, as pitching moment is zero for ...
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2answers
817 views

Does an increase in lift always cause an increase in lift-induced drag?

An increase in lift causes an increase in drag. Is it always true? I am confused with two points. Lift increases with an increase in airspeed but induced drag reduces with an increase in airspeed. ...
0
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1answer
58 views

What is area in equation of lift?Does it remain constant during flight? [duplicate]

I am beginner & learning aerodynamics concept. What is area in equation of lift(L) =Coffecient of lift x area x density x square of velocity/2. Does increase in angle of attack increases the area &...
5
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2answers
387 views

What is Neil Armstrong teaching in this image?

It seems to me that in this image Neil Armstrong is teaching something related with aerodynamics forces (lift, drag...), but I don't know exactly what is that "Triangle" that He drew (It doesn't seem ...
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1answer
92 views

How much might soft skin reduce aircraft skin friction?

According to Peter Kampf's answer here, soft skin can damp a (vibrational?) mode that cause laminar flow to become turbulent. Thus, it could help delay boundary layer transition. My question is, for a ...
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0answers
59 views

What are the variables of the induced drag formula and where does this force apply?

I want to understand a little bit more the induced drag force, therefore in analyzing the formula: $$ F_D = C_DA\frac{⍴V^2}{2} $$ what do the following variables actually mean? $ F_D $ Is the 3D ...
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4answers
229 views

How high does the “bug layer” extend?

As far as I know, a big obstacle to attaining laminar flow in aircraft today is the so-called "bug layer", presumably a lower layer of the atmosphere where bugs are encountered. So, my question is ...
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1answer
102 views

Helicopter Basics: How does lead-lag of blades actually help in compensating for increase/decrease in speed due to flapping?

I understand the following - Due to dissymmetry of lift, flapping up and down occurs. Since angular momentum has to be conserved, the speed of blade increases/decreases during flapping up/down ...
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1answer
153 views

At which point in scale reduction do slats and flaps become unnecessary?

Imagine some Fi-156 Storch, and reduce its scale down gradually to 10cm span. Let's assume full scale Fiesler Storch is 100% efficient at, for example, minimizing stall speed. During this reduction ...
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2answers
3k views

Does an F/A-18 require a lot of rudder in turns?

I am an aspiring Navy fighter pilot and I use an X-Plane add on for FA-18 Hornet as a fighter. It's made by a creator named Colimata. I think the turns are unrealistic. When I begin a bank a lot of ...
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0answers
72 views

How to create a simple forces diagram using only lift and drag forces?

I would like to create a simple forces diagram (like a sketch). The lift produced by the wing depends upon to the distance from the the longitudinal axis, but, in order to make it easier, I’m taking ...
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1answer
48 views

What does induced flow exactly means on helicopters flight? How is it different from downward deflection of air?

I believe all airfoils deflect air downwards at an angle at a velocity V. What is the difference between the downward-vertical component of the deflected wind and the induced velocity in Helicopter ...
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0answers
24 views

How is the wingspan of a wing measured if it has a dihedral? [duplicate]

I am having some confusion regarding how the wingspan is measured, I just wanted some clarity because this was bugging me while I was reading about aircraft wings. According to NASA's "Wing Geometry ...
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2answers
45 views

How can we physically define reynold number variation in terms of characteristic length? [closed]

How can you define it physically that greater the characteristic length in $Re=\frac{\rho v L_c}{\mu}$ greater the Reynolds number. Like on wing surface $Re$ is higher than the horizontal tail surface ...
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1answer
62 views

What causes lift in aerofoil: Bernouli's principle or Newton's third law? [duplicate]

Reading materials online, I observe some explanation based on Bernoulli's principle, quoting the difference of air pressure above/below and difference of speed of airflow. While some say's Bernoulli's ...
2
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2answers
290 views

Helicopter flight: Does the rotor disc plane and hub plane rotate along axis perpendicular to rotational axis?

In many pieces of literature, diagrams as below are shown to explain the directional flight of Helicopter. I have the understanding that the cyclic input will only change the pitch angle of the blades ...
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3answers
412 views

Do adding high thrust in plane prevents it from stalling?

I am convinced that fighter jets (every flying object) do stall. So from quora, Why don't fighter jets stall? But most of the fighters have thrust:Weight ratio > 1 which means that they are not ...

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