# Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

1,154 questions
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### Propeller Efficiency calculation different by two methods

Please refer to this MIT page which I used for my calculations: https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node86.html I calculated my aircraft propeller's prop, thrust, and torque ...
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### Transonic buffet - reason for a rapid movements of the shockwave along the wing chord line?

I know that transonic aerodynamic buffet is caused by the separated turbulent boundary layer striking the airframe (horizontal stabilizer, wings, fuselage) with considerable force causing a high ...
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### Is it possible to estimate the location of aerodynamic center without experimental moment data?

In airfoils, the aerodynamic center is usually found close to the quarter chord point, but for quick calculations, we assume it lies on the quarter chord. What I am looking for, is if there is any ...
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### Why is the delta wing naturally stable in pitch?

Any thoughts on why the delta wings are naturally more stable in pitch, so they don't require any tail surface? What's the physics behind this?
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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 happens aerodynamically when we trim an aircraft?

I'm trying to understand stability & control. Please correct me if I'm mistaken. An aircraft will have longitudinal stability if the aerodynamic center (AC) is behind the center of gravity (CG). ...
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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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### Why does a turbulent boundary layer cause more friction drag than a laminar boundary layer?

From what I understand, friction is caused by viscosity and a bigger Reynolds number signifies lower viscosity. Thus, a higher Reynolds number(i.e. turbulent flow) results in lower friction. But, ...
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### What is the correct procedure in case of vertical stabilizer failure?

What is the correct procedure in case of vertical stabilizer failure in cruise? Am I correct in guessing that one should descend to a lower altitude and decrease speed?
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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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### Velocity of air flow around aerofoil

To find the velocity of the air flow at each section of the aerofoil, am I right to say that the horizonatal velocity of the air flow is constant throughout the chord while the vertical component of ...
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### What is primary cause of shock induced separation (shock stall)?

In the video link above describing Prandtl Meyer Waves, lecturer stated (at 22:40) a very important fact on which he based his first half of the lecture. "Mach wave (mach lines) deflect the flow ...
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### Why is the A380 a double-decker rather than a longer airplane?

It seems like making the A380 a double-decker increases the cross-sectional area of the fuselage, thereby increasing drag on the airplane. Wouldn't it be more efficient to fit so many seats in a ...
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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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### Why is an elliptical wing planform so aerodynamically efficient in layman's terms?

Below is part of an answer to the post 'For the elliptical wing, what is elliptical, and why is drag regularly distributed?': On the untwisted elliptical wing the local lift coefficient is constant ...
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### Why does a rectangular wing stall first at the root?

Why does a rectangular wing stall first at the root? as opposed to tapering of the wing which causes the stall at the tip and moving inboard?
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### What are the two turning tendencies that occur during a steep turn?

A question has come up in preparation for a Block exam. what are the two turning tendencies that occur during steep turn? If you know this may you please explain to me, why these tendencies occur. ...
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### Why does a stall decrease lift, rather than increasing it?

A stall occurs when the angle of attack of a wing or other airfoil becomes so high that the airflow over the upper surface of the wing separates from the wing, rather than remaining attached to it; ...
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### Can this vane prevent/delay wing stall?

Given that a stall results from the airflow over the top of the wing separating from the wing at high angles of attack, would it be possible to prevent, or at least ameliorate, a stall by deflecting ...
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### Do swept back wings affect the moment of inertia of an aircraft enough to be relevant for the roll response?

I have studied that swept back wings help in delaying the shock waves formed on the wing, but also to my understanding I feel swept back wings reduce the moment of inertia (like for example a ...
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### Do stall strips mean that wing washout is not required?

The Wikipedia page on stall strips states that AA-1 Yankee airplanes used stall strips to avoid tip stalls (and spins) because wing washout couldn't be used. So my question is: can two stall strips ...
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### How do rotorcraft achieve lift?

How do rotorcraft (helicopters, and other rotary aircraft etc.) achieve lift? I mean, obviously the rotor. But who knows the specifics? What are the physical, mechanical requirements of a rotary ...
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### How do the vortices affect the flow of the horizontal stabilizer upon leaving the wing?

Other than the downwash effect, what other factors that affect the flow to the horizontal stabilizer? such as Dynamic Pressure? Air Flow Disturbance?
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### Why don't more airplanes incorporate spiroid winglets? [duplicate]

In typical airplanes, lift induced drag can account for the majority of the overall drag. Why don't more aircraft employ methods to reduce this and specifically why not spiroid winglets? From every ...
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### How do planes respond aerodynamically when bringing them into inverted flight by rolling?

For the sake of the question the plane is fully capable of inverted flight, no problems with engines etc. Background of the question is the observation that the airflow around the wing must also ...
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### How do the vortices of a fixed wing and horizontal stabilizer interact? [duplicate]

What interaction of vortices between the fixed wing and horizontal stabilizer? How do the vortices affect the flow of the horizontal stabilizer upon leaving the wing? when will the downwash effort ...
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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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### Why does the angle of descent increase in a constant headwind while decreases in a sudden encounter with a headwind, in a descend?

I'm currently studying aerodynamics. I have realized that a sudden encounter with a headwind during descent will result in the aircraft generating more lift, thus angle of descent decreases. I haven'...
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### Is lift in fact a kind of drag?

Given the similarities between Lift and drag and their very similar relationships to the density, surface area, and airflow velocity, could one, in theory, describe aerodynamic lift as a kind of drag ...
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### Does Buoyant Lift Force scale with Load Factor?

Let's say I am flying an airplane that has a weight of 100,000 kg with a 1G load factor at normal steady flight. I have helium lift assist that is providing 50,000 kg (50%) worth of buoyant lift force ...
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### Where can I find the best site to learn aircraft design on a small scale? [closed]

I am undergraduate student still trying to figure out a lot about Aerodynamics and aircraft design. I am learning how to design rc planes. So the thing I know the weight of my plane which is between ...
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### Why does an elevator deflection (step) result in a nonzero short-term-steady-state response in pitch rate?

I know from the simplified Short Period linearized equations (state space with Angle of Attack ($\alpha$) and Pitch Rate ($q$) as states) that the steady-state value of the pitch rate response to ...
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### Why do some airplanes have simultaneously a straight wing and a swept horizontal stabilizer?

I'm sure there are many other examples like this one: Embraer EMB 120 with an almost straight wing and an obviously swept horizontal stabilizer. Why is there a difference in sweep angle between the ...
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### How to best recover from an excessive descent?

Suppose I found myself in a rapid, steep descent, perhaps right after breaking a spin. E.g. a 60 degree nose down with 100kt and accelerating rapidly, on a Cessna 172. What might be an ideal ...
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### How do I decide the tail dimensions and the distance between the wings for a bi plane? [closed]

So I am designing a biplane,I know the weight.I want to know what is the lift formula , volume ratio and aspect ratio for a biplane? I know the formulas for monoplane
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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 (or where) do I find an airfoil optimized for low reynolds numbers (100,000~150,000)?

Looking to build a RC plane. Because the span is going to be small and the speed relatively low, I estimate the R-number to be around 100,000. Is there an airfoil optimized for that range of Reynold's ...
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### What are dimensions of the B-17 propellers?

I'm curious about the aerodynamics of the Boeing B-17 propeller, as the proportions looks perfect for a project I'm working up. Does anyone out there know where to find the specs/dimensions/models for ...
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### How does setting takeoff flaps improve aircraft performance?

A study guide I recently found indicates that Vmc and aircraft performance improve with takeoff flaps set. The Vmc improvement makes sense but the performance improvement does not. At a basic level, ...
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I am still confused whether a head wind or tailwind would affect the rate of climb. Since in a HW/TW condition our a/c is basically still climbing in the same parcel of air, it is just that parcel of ...
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### Why are fighter jets equipped with dorsal fin?

I don't really get whats the purpose of dorsal fins and what they do with the flow over the vertical stabilizer. I noticed on most single tail configured aircrafts are equipped with a dorsal fin like ...
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### What does the extending the flaps do (or any high lift device) to the Rate-Of-Descent of an airplane?

I know that deploying flaps will increase both drag and lift, thus increasing L/D ratio. But how exactly does that correlate with the increase/decrease of the rate-of-descent?
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### What effect does downwash have on the horizontal stabilizer

Fighter aircrafts usually have their horizontal stabilizers in lined with the main wing which would subject it to downwash. How does this effect the stability of the aircrafts and the effectiveness of ...
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### What can cause a sudden jump in Indicated Air Speed?

My aircraft heading is 321 with constant Static pressure, wind speed and steadily increasing Ground Speed. Meanwhile, there was a sudden jump of 10kts in IAS from 140 to 150 kts withing a span of 1 ...
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### What are the benefits of “fixed wing with different swept angles on the trailing edge”? [duplicate]

Take Boeing 767's wing's trailing edge for example, it starts at the root with being perpendicular to the fuselage, then it swept back like the leading edge. What is the technical term used for this ...
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### Definition of a Deep Stall

I've been doing some research for a uni assignment and I noticed that the RQ-11B uses a "deep stall landing" to get back onto the ground. What I don't understand though is how this aircraft gets into ...
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### Why is polar curve of a glider dependent on flight load?

This is my first question here. I'm just a glider in education phase and not yet a pilot, but because I'm also physicist, I'm interested in some details more than other people. My question is simple:...
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### What is the relation between flap setting and aileron droop on the A350?

The A350 has a aileron droop function, which is linked to the flap setting. In contrast to other aircraft with aileron droop, the A350s ailerons do not droop when the flaps are fully extended. I ...