# 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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### Why will the max lift point not be at the center of a swept but constant chord wing?

(In this question when I say "swept wing" it means the blue wing seen at the bottom. So no fuselage or anything) If you look at this graph from this answer, you'll see the max lift point of ...
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### Understanding the constant speed prop and 2-4 degrees optimum

I've read through some answers on here and just wanted to write my own description of how this works and let someone check for me. Currently I've just started to fly an King air 100 with PT6A We ...
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### What happens in order to make a shock when the flow first turns?

Imagine you have a really zoomed in view of a 2d ramp, which is at 20 degrees. Zoom in on the exact point the ramp turns from horizontal to 20 degrees. When the first supersonic air molecules reach ...
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### Why will the pressure distribution of a swept wing promote stall?

Here it explains how the bound vortex will change the lift distribution of a wing. What is meant by the lift distribution changing is that there is less lift at the tip, meaning the pressure ...
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### How does the downwash behind a swept wing differ from a normal wing?

How does the downwash behind a swept wing differ from a normal wing? (I know you can’t trust everything you see on the internet, but this seemed legitimate) Here it said: The downwash pattern on a ...
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### Why are shockwaves allowed different angles at different distances from a body?

It's been (well) established that a shockwave can only be at the angle of the Mach cone. (I now understand this part). However, in this picture: you can see that the shock is at 2 angles. I also ...
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### Why will a slower moving parcel of air above a wing create drag in non-inviscid flow?

This answer explains why a thicker boundary layer will cause a type of form drag. It uses inviscid flow to explain this. It is a great answer, but I can't seem to see how this applies in a real world ...
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### How does a thickening boundary layer create form drag?

Imagine a normal wing with flow over it, and to simplify things it's at 0 AoA. Drag is being made mainly because of form drag and skin friction drag. I'm not sure on this, but I don't think there ...
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### What's gonna be the physics behind building 'futuristic' airplanes? Use physics formulas or even theories to answer this question [closed]

After thinking about these 'futuristic' airplanes, I wonder if there's any special physics theory or law behind them. I wonder how faster they can be, persevere more and fulfill the aviation's lover ...
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### Why don’t closed wings eliminate tip vortices?

It’s clear that tip vortices never really can be prevented, but why doesn’t a closed wing do that? There is no ‘tip’ on a closed wing so where does the air go to make a vortex? On a normal plane the ...
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### Gap between F22 ailerons and flaperons

You can see in the below picture that there's an F22 on approach (I think) and this is almost a perfect bottom view of the plane while it's going straight, it isn't banking. There's gaps between the ...
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### Lateral Stability- Why aircraft will not return of its own accord to the original heading after a sideway gust?

I am reading the Stability section of FAA it says: If an aircraft is flying in a straight line, and a sideward gust of air gives the aircraft a slight rotation about its vertical axis (i.e., the ...
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### Why will the flow turning angle be 0 (or close to) inside of the Mach cone?

(Disclaimer : This probably seems like my 56th question on the same topic, but this will be my last relating to Mach cone angle and shock angles, as I think I understand most of the topic) So the ...
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### Could a propeller system for airplanes with automatic, cyclic blade-pitch control that is designed to counter p-factor be practical?

Considering that P-factor is a result of differing angles of attack of the blades on an airplane's propeller, I would imagine that if there was a design that could control the pitch of each individual ...
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### What are those little pieces for on the C27J?

Here is a picture I took. You can see some pieces on the vertical stabilizer, but only on one side. I imagine this is for an aerodynamic purpose, but I am not sure. What do you think about its purpose?...
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### F15 Startup Intake drop

So I’m aware that the F15 has intake Ramps that adjust to airspeed and AOA, in order to ensure that the airflow is entering the engine smoothly and not too fast. But why does the system drop the first ...
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### Can smaller wing area improve the aircraft experience during turbulence?

Amid the recent incident of Singapore Airlines flight 321, leaving one dead after a severe turbulence, I ask myself if having an aircraft with smaller total area, there is less turbulent air that ...
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### Can a shock in certain circumstances be at a lesser angle than the Mach cone?

(Excuse the drawing quality) What will happen if a shockwave has an angle less than that of the Mach cone? In this picture, the black line represents the Mach cone. The orange line represents the ...
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### Does the flow turning amount change as you get further away from an object?

Will the flow turning amount change as you get further away from an object? This answer explains why shockwaves will extend past the body that made them (good starting point). This question is asking ...
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### Lift without aerofoil? [duplicate]

I have seen some RC planes flying without any form of airfoil, the wing is literally a flat board. What I want to understand is how lift is generated under these conditions. I understand kinetic ...
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### Why does the angle of a shock change when the flow leaves the influence area of an object?

In this (great) answer, it says: "far enough" from the Concorde's nose, the path followed by the airflow is not affected by its presence and it's just a straight line. Close to the nose we ...
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I understand wind direction can vary in a column of air? With only altitude control on a blimp to navigate for long flights, a blimp in theory could navigate without engines. In order to take real ...
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### What is the main reason raked wingtips are more efficient than winglets? [duplicate]

What is the main reason that these: Are more efficient than these?: My main guess is that they improve L/D compared to winglets, as they provide more upwards lift making them more efficient. It ...
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### Angle of bank affects on descent rate

I’m attempting to do some maths regarding the ‘impossible turn’ (engine failure after takeoff, followed by a 180+ deg turn back to the field to land). I understand how to determine radius, rate of ...
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### Why does the shock angle always seem to equal the "sound cone" angle?

(I'm going to use the term "sound cone" for the area you can hear an aircraft when it's at Mach ≥ 1, illustrated by this picture. Not considering the shockwave.) So as explained in this ...
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### Can a sound wave travel through a shockwave?

Say you have a scenario where there is a shockwave, and you sent a normal sound wave towards it. Could the sound wave travel through that shockwave? If so/not, why? Would it depend on the strength of ...
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### induced drag at supersonic speed [duplicate]

for a delta wing with supersonic leading edge at small angle of attack there is no stagnation point on leading edge so There is no connection between the top and bottom of the wing. Therefore, the air ...
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### Why does adding heat to the subsonic flow increase the speed of the flow?

In Rayleigh flow, adding heat to the subsonic flow increases the speed and adding heat to the supersonic flow decreases the speed. But what is its physical cause?
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### Why Cessna 152 has different airfoils at the root versus at the tip of the wing?

I recently read that C152 have two different airfoils on its wing. NACA 2412 at the wing root and NACA 0012 the wingtip. Why? And why are those particular airfoils (with their inherent aerodynamic ...
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### Lift Coefficient question

I am making a RC Airplane, it has a wing profile as shown above. What might be the approx. lift coefficient of this? The wingspan is 80cm, what will the lift provided be by this wing at 65kmph ?
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### Does separation happen easier with less dense air?

Does less dense air affect when separation happens? So if you have a cylinder traveling in a straight path like the one above, there is separation happening at a given speed. If you were to change ...
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### Can there be interference drag in inviscid flow?

I understand that interference drag is the difference between the terms: the total drag of a configuration, and the sum of the individual drags of the components in the configuration. (It exists due ...
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### Can a wind gust below the rotor affect the lift force in a helicopter?

If a helicopter is hovering and a very strong, narrow and focused wind gust comes from the front and passes few feet below the rotor blade without touching the fuselage or any part of the aircraft for ...
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### Cessna 152 rattling/clanking noise in tail?

Going on a flight in a c152. Upon taxiing we hear a relatively loud and noticeable clanking/banging noise from what sounds like the tail. Never heard it before till this flight. Upon takeoff the noise ...
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### Does weight of an aircraft affect its ability to pull G?

This question includes the quote: A C42 doesn't weigh much, so to pull the 5+ G required to exceed the design specifications of it's wing spar and fixings would require extreme speeds. I'm not an ...
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### Why doesn’t the air expanding behind a shockwave reverse the effects of wave drag?

Wave drag is (from my understanding) the difference in pressure between the front and rear of an object due to shockwaves, making an opposing force. This needs higher pressure in front of said object ...
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### Are rectangular fuselages more sensitive to winds than circular ones?

If you have an aircraft like the DHC6 twin otter or the SkyCourier (picture bellow which have a rectangular shape like fuselage) and then you have another aircraft with the exact same dimensions and ...
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### How does the lift-to-drag ratio depend on absolute sizes?

A dependency is provided here $$(L/D)_{\max} = \frac{1}{2} \sqrt{\frac{\pi \varepsilon ~ \mathrm{AR}}{C_{D,0}}}$$ AR significantly affects the outcome in this dependency. AR varies significantly among ...
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### Range, Endurance and Fuel Cost Savings of an Aircraft

I have recently carried out CFD simulations on the A320 fuselage and modified its fuselage. I did this by matching the Reynold's number of the cruising altitude. The reference values were taken at ...
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### Why are the top of the F/A-18 strakes curved?

As seen in this picture, the top of the strake has a slight curve to it. I'm mainly talking about the curve seen if you were to look at it straight on. To be more clear, not the curve of the strake as ...
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### Anyone come across a concept of vertical spoilers on wings not perpendicular to the flow? As in not following the LE/TE sweep direction?

For reference, I am currently investigating vertically actuated spoilers for gust load alleviation for my master's thesis, and I was wondering, if the concept of non perpendicularly oriented spoilers ...
1 vote
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### Can partial flow separation make the effects of Reynolds number on stall more significant?

While discussing this stall differences with altitude question with a skydiving canopy designer, I told him that most people seemed to think Reynolds would not be significant at these altitudes. His ...
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### Does partial flow separation due to toggle input affect the physics of paraglider/ canopy controls?

A skydiving canopy designer said the following: Airflow is separated even before stall on a big portion of the canopy.... It's specific to [the] way toggle[s] distort the trailing edge. Is this true,...
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### How does ground effect work with a banked wing?

How would an explanation of ground effect such as this one from Peter Kämpf be modified to account for a highly banked wing? A paraglider and HP canopy pilot told me that when he banks a wing to touch ...
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### Why would there be a drag discrepency when simulating transonic flow over scaled CRM geometry?

I have a discrepancy when simulating a wind tunnel experiment of a 2.7% scaled NASA CRM geometry as used in the wind tunnel. I am trying to replicate exactly the wind tunnel model and flow conditions ...
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### Estimate the drag caused by wind on a free falling body

I'm trying to solve the following problem for my masters thesis: Estimate the drag caused by wind on a free falling body from H altitude. H is in range of 300-1000 meters. What would be the best way ...
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### What is the main cause of pressure recovery on airfoil?

What is the main cause of pressure recovery over a wing? I’ve narrowed it down to be one of or a combination of 2 things: The higher pressure air from the bottom of the wing equalizing with the upper ...
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### Does the back pressure on an airfoil stay the same with different speed?

(Inspired by this answer) The back pressure is the force on the rear side of an airfoil (in the pressure recovery zone). When the air streams reach the pressure recovery area on an airfoil, they are ...
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### Why do shocks travel further down the wing as the Mach number increases?

Inspired by this question, why do shocks move further back on a wing as the Mach number increases? Normal shocks on the surfaces of wings form when the air molecules of the pressure recovery area on ...
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