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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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4answers
215 views

In general, how do aircraft handle differently in inverted flight versus in upright flight?

Inverted flight is flight with a roll angle between 90° and 270° (although it classically referred specifically to flight with a roll angle of 180° - i.e., upside-down). In what ways, in general, ...
2
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5answers
308 views

Is the aircraft neutral point a function of the tail incidence angle?

While using XFLR v5 for a basic analysis I am facing this issue. For a fixed configuration I varied the tail incidence angle and XFLR is displaying a change in the Neutral point location. But as per ...
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1answer
121 views

Why does the Aurora D8 have vents on the bottom of its fuselage?

The Aurora D8 is a concept of an experimental aircraft (not an actual aircraft for now), described in this site. It's discussed in this question here on Aviation.SX. I was watching the embedded video ...
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0answers
84 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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2answers
109 views

How is a propeller diameter for given application determined?

let's say I need 1000 N of thrust for a given aircraft and flight velocity. I have available a fixed pitch propeller with a given shape, and thus given performance to advance ratio curves. Let's say ...
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0answers
59 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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1answer
69 views

What is the relation between hinge moment at the control surface and servo torque? [closed]

I am trying to estimate the required servo torque for my design using hinge moment at the elevator. XFOIL results were as follows- I am getting a Hinge moment of about 0.06-0.08 Nm. for the given ...
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1answer
144 views

Difference between Mach buffet and shock stall

What is the difference between Mach buffet and shock stall?
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3answers
331 views

What has happened to make me experience negative G with the control stick FULL AFT near the top of a loop?

I experienced negative G with the control stick FULL AFT near the top of a loop. My questions: Aerodynamically, what happened? Was the wing meeting the air at a negative-lift angle-of-attack (...
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0answers
43 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 ...
1
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0answers
52 views

Induced drag - inverse proportion between induced drag and parasitic drag [duplicate]

I recently learned that the slower an aircraft is traveling, the higher the induced drag and the lower the parasitic drag. The parasitic drag is lower because the particles have less force against the ...
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2answers
161 views

Propeller Characteristics at Different Altitudes

Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars ...
2
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1answer
58 views

Accounting for torsional forces during wing load tests

According to this aviation.se question, wing load tests are done by placing weights on the wings (upside down). This unfortunately only tests the wings bending loads (for cantilever wings) and the ...
4
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1answer
213 views

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 ...
8
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2answers
248 views

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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1answer
108 views

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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1answer
168 views

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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0answers
59 views

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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2answers
295 views

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). ...
2
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0answers
102 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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3answers
239 views

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, ...
5
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3answers
314 views

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?
2
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0answers
52 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 ...
3
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2answers
116 views

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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1answer
250 views

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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3answers
592 views

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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0answers
31 views

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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1answer
296 views

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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1answer
1k views

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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2answers
163 views

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. ...
14
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5answers
4k views

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; ...
6
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1answer
179 views

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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5answers
312 views

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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2answers
199 views

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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2answers
74 views

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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1answer
66 views

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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0answers
236 views

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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3answers
514 views

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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1answer
108 views

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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0answers
78 views

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" ...
4
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3answers
289 views

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'...
14
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6answers
3k views

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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3answers
128 views

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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2answers
94 views

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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1answer
105 views

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 ...
13
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2answers
2k views

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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3answers
238 views

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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1answer
193 views

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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0answers
595 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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1answer
83 views

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 ...