Questions tagged [aerodynamics]

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Why do air-to-air missiles have tail fins?

That sounds like a stupid question but hear me out. For something like a rocket where the goal is to fly in a straight line the use of the tail fins is obvious. But air-to-air missiles are designed to ...
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What aerodynamic equation should be used to determine the drop in air pressure over an airfoil embedded within a vertical pipe?

I have a conceptual idea for a thruster for a VTOL aircraft/drone which should produce lift by utilizing a upward-flowing airflow to produce low air pressure over the top surface of an airfoil that is ...
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is there a difference in performance between these two fan designs

These two fans are usually used in hairdryer is there a difference between them in performance if both have same rpm and same outer diameter.
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1 vote
1 answer
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Where is best place to install vortex generators if race car diffuser stall?

If flow separate in high AoA diffuser, vortex generators can help to delay separation. Where is best palce to install VG for flat floor + diffuser configuration , in front leading edge of diffuser or ...
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What are the advantages of an asymmetrical missile nose cone?

Some rocket- and missile designs sport an asymmetrically conical nose cone. A prime example being the Stunner missile in "David's Sling" surface-to-air system. Several sources (such as ...
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2 answers
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What are the practical applications of Centre of Mass & Centre of Gravity?

I have learnt COM and COG are different things if we have non uniform gravitational field i.e. mass will be same at anywhere but gravity will be different. I want to find practical examples of both ...
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2 votes
3 answers
87 views

Why wind turbine dont use high lift coefficient airfoils?

All wind turibne use low lift coefficent airfoils from 1.0 to 1.5. Why not use high CL airfoils to get maximum torque? http://airfoiltools.com/airfoil/details?airfoil=s812-nr
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3 answers
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Is the main goal for wind turbines to take maximum energy for a given diameter?

If you increase the number of blades, that will increase torque, for the same RPM you get more power,...simple logic So why only three blades, is main goal for wind turbine take maximum energy for ...
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2 answers
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Kelvin's Circulation theorem applied to a cup of tea

Recently, I dipped my spoon into my tea. I saw that as I dipped my spoon into my tea, two vortices formed at both edges of the spoon. I guess this is similar to vortices forming at the end of ...
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3 answers
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Is the drag coefficient/velocity of of a vehicle based on frontal area?

Does the frontal area of a vehicle determine the velocity/drag coefficient of a car? A Ferrari 458 has a Cd of 0.33 while a Corvette C6 has a Cd of 0.29. Does this mean the Corvette will have less ...
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1 answer
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Convert from mm of water to Coefficient of pressure (Cp) [closed]

Okay, I have this value in mmH2O (2.650) and am not sure where to go next to convert it to aerodynamic parameter pressure coefficient please? mmH2O * 9.8066 = N/m2 ???? What do do next please? I ...
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-2 votes
2 answers
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How can a car travelling at a higher speed may cause it to lift off from the ground?

Many Sports cars and other high speed and performance ground vehicles have a rear wing attached to its rear, and a splitter attached to its front. From what I understand, the rear wing (which takes ...
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Vortex diameter

There exists clear definitions of the size of a vortex core, but vortices affects it surroundings beyond this core. An example is a wing tip vortex which has a small core, but can be seen as a big ...
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How to determine the stability of an aerodynamic shape in ANSYS Fluent

I have the aerodynamic outer mold line file of a drone. The first task of the school project is to verify that the drone is stable. First, I used the 2021R2 version of ANSYS Fluent to try to find the ...
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1 answer
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Why flow around an airplane is different in different frames of reference

In the book Fluid Mechanics by Yunus Cengel it was written "Flow around an airplane, for example, is always unsteady with respect to the ground, but it is steady with respect to a frame of ...
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Are there any methods to figure out how aerodynamic a race car is without a Cd number?

For the top speed of a car, I believe it's usually limited by drag and horsepower. However, I've also learned that gearing can affect the top speed and acceleration of a car. Are there any methods to ...
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1 vote
3 answers
512 views

Does more downforce affect the acceleration and top speed?

How can downforce make a race car faster, apart from being faster around corners? I just recently learned that downforce can help a car accelerate from 0-60 mph faster. Usually, I thought drag didn't ...
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1 vote
3 answers
214 views

What affects a car's overall top speed?

I've always wanted to know how a car's top speed could be determined. Usually, I thought it was horsepower and aerodynamic drag. I learned that weight can affect top speed, but I've recently found out ...
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26 votes
4 answers
6k views

How can a piece of paper be shaped to guarantee it falls slower than a plain sheet of paper?

My son and I are playing "MAKE" (think "HORSE") and we challenged ourselves to build the slowest falling object using only a sheet of paper. We cannot build anything that falls ...
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2 answers
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How long does it take and how far does it travel a sphere in free fall before reaching a percentage of the terminal velocity?

Assume a sphere (hail) that is free dropping in air. At some the sphere will reach close to the terminal velocity. The question is: how long $t_p$ in seconds does it take before a percentage $p$ of ...
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1 vote
1 answer
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Does the terminal velocity of a sphere in free drop increase with increasing diameter?

I was trying today to calculate the terminal velocity of a hailstones with increasing diameter and mass. I was trying to figure out if larger hailstones will have a higher impact velocity or lower. I ...
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What is the velocity of a fluid particle at the center of a infinitely long counter-rotating vortex pair?

Let's take circulation strength of each vortex τ and distance between them is r. I feel the answer should be 2τ/πr but my friend is arguing its τ/2πr. So my thought process goes like, if you have a ...
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0 votes
2 answers
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Will a lift force be created by the Coanda effect if high velocity air flows under a half-toroid shaped saucer? [duplicate]

I would like to know if a lift force will be created by the Coanda effect from high velocity air that is directed under a half-toroid shaped saucer by a centrifugal impeller. To illustrate how such a ...
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1 vote
1 answer
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What is the side way force on a flat membrane place perpendicular to the flow of current on one side, and stagnant water on the other

So basically imagine a plate being placed parallel to the direction of flow of water with water flowing with a certain velocity on one side of the plate and on the other side it is almost stagnant. ...
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1 vote
0 answers
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How to properly use the lift-curve slope for divergence calculations?

I was reading Wright and Cooper's writings on static aeroelasticity and I think I'm missing something. To calculate the acting lift, the equation $L = q S a_1 \theta_0$ is used, where $q$ is the ...
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Which of these propeller configurations is most efficient?

All propellers shown in the figure above are identical and are operated at identical speeds with four separate (numbered 1 through 4 vertically) configurations illustrated. The physical distance ...
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1 vote
1 answer
43 views

Why don't we use feather like structures for hang gliding?

I'm not entirely sure if this is the right site for this question, but I recently went on a Greek Myth Binge and came across Daedalus again, and his famous first hanglider, made from feathers. Now, ...
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2 answers
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Is it known how streamlined the Shinkansen 800 bullet train is when on rails?

This question is different from What is the optimal streamlined shape?. That question is probably about an ideal situation of flowing through space with no gravity in a fluid with zero viscosity and ...
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Wind behavior and pattern

From the 5 options, which one shows the worse wind effect? Is it (b) because wind speeds accelerate through a gap? But how about in comparison to (c)? Or (d) due to the height and sharp corners? If it'...
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2 votes
0 answers
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Convergence problem in RANS simulation of unsteady flow

I am simulating an air flow through a two dimensional rectangular channel. The channel splits into two channels, one of them is followed by a 90 degree bend downwards and leads into a cylindrical ...
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0 answers
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Why does the tapered part of a Wing have such high coefficient of Lift?

If we take a Trapezoid wing shape as an example and see that it has low $c_l$ near the root of the wing and very high $c_l$ at the tip. The Lift generated, however, is reversed to the that of the $c_l$...
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1 vote
2 answers
246 views

Is air density calculated using Total Pressure (Dynamic and Ambient) or just Ambient?

I have some wind tunnel data and static and dynamic pressure are logged (temperature too). I need to calculate lift and drag but I’ve been confused whether to use only ambient pressure to calculate ...
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1 vote
2 answers
102 views

Why does flow separation cause stall when it creates a low pressure zone?

In an airfoil, a low-pressure region forms in the turbulent wake created when the flow separates. Wouldn't this cause an increase in the net vertical force acting on the airfoil since the pressure at ...
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1 answer
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How to do Blade Element Momentum Theory Analysis for NACA airfoils?

I wanna perform BEMT analysis on blades of different geometry and not just symmetric thin airfoil. How to do this?
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1 vote
1 answer
55 views

Extracting Uncertainty from Numerical Solution

I am performing numerical and uncertainty analysis for an oblique shockwave angle function: $$ \tan(\delta)=\frac{2}{\tan(\theta)}\frac{M^2\sin^2(\theta)-1}{M^2(\gamma+\cos(2\theta))+2} $$ where $\...
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1 vote
2 answers
109 views

why do centrifugal compressors have curved blades?

Why are centrifugal air compressors built with backward curving blades?
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-1 votes
1 answer
33 views

What is the most efficient way to heat air?

I'm currently playing with a school project. My goal here is to heat a stream of air to a significant temperature so I can demonstrate air expansion. I have a cylinder, with a few turbines, turning in ...
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3 votes
0 answers
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How does NASA's QueSST X-59 jet work?

The QueSST (Quiet Supersonic Transport) is a project to create a more diffuse sonic boom in order to use supersonic flight commercially without the usual abrupt 1~2 psf pressure spike damaging the ...
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0 votes
1 answer
290 views

Would this air amplifier attachment increase a leaf blower's effectiveness?

With the start of the leaf raking/blowing season just a month away, I have been thinking of a way in which I could make my old leaf blower more effective so I can spend less time doing leaf blowing. I ...
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-1 votes
1 answer
86 views

What is pitch stability in cars?

Can reduction in pitching moment of a car be referred to as improved pitch stability? Or is this term strictly only with regards to aircrafts?
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4 votes
1 answer
928 views

How does a helicopter hover

I am wondering how a helicopter manages to stay balanced and stay in one spot while it is in the air. I understand that there is a second rotor that is used to counteract the angular momentum and also ...
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1 answer
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How far downwind of a Covid-19 emitter has a 1000-fold reduction in PPM?

How far downwind of a Covid-19 emitter has a 1000-fold reduction in PPM? Assuming that Covid-19 (0.12μm diameter) particles have the aerodynamic properties of a gas: Particles < 20 μm behave same ...
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-1 votes
1 answer
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Does a V shape of quadcopter rotors give stability?

If I build a quad copter but angle each rotor slightly inwards, should it be self stabilizing like an aeroplane with V wings, or does a variation of the rocket pendulum fallacy apply here? I feel like ...
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-1 votes
1 answer
43 views

Stagnation,static and dynamic pressures

Please can someone help out with the actual concept of stagnation,static and dynamic pressures . I have learnt all that stagnation pressure is when velocity of flow is 0 when isentropically stopped ...
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1 vote
0 answers
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Superimposing a Vector Field onto a Toroid in Matlab

I am a systems and control PhD student in Aerospace Engineering. Currently, I am trying to create a wind shear model of a toroidal thermal "bubble" in Matlab similar to the one in this paper (shown ...
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-1 votes
2 answers
54 views

How to make a oblique wing without areodynamics skill?

Is it possible to make a oblique wing just by skewing a profile of a standard wing? Take a wing profile from web Divide it in sagittal slices Move slices along a new axis (still lying on horizontal ...
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-1 votes
1 answer
58 views

Does the shape of a car really matter for how much gasoline it drinks?

Let's say that we have a mid-1950s "gas guzzler". Now, we take away the exterior "shell"/chassis and replace it with a modern car's. That is, it will visually look just like a modern car from the ...
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3 votes
0 answers
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Mathematical transformation of a heading angle to a roll angle

I'm trying to understand a function in a SIMULINK example of a path following UAV simulation. The gist is that, the UAV Waypoint Follower block provides a required heading from a list of waypoints and ...
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-1 votes
1 answer
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Efficiency of propeller with Wind perpendicular to rotation axis

What happens to air flow and propeller efficiency if it is moving with Wind perpendicular to rotation axis. The air is blowing in a direction lying on the Planet of the tips.
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2 votes
1 answer
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Why is it when taking the moment coefficient relative to c.o.p., the weight is ignored?

I have been working on a question, and my lecturer has hinted me with this equation that doesn't include forces due to weight? $C_{M_x}=C_{M_{ac}}+C_L(x/c−x_{ac}/c)$ What he told us was that due to ...
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