# Questions tagged [aerodynamics]

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### How do drag and downforce in a rear spoiler of a car vary with angle of attack?

I ran an two aerodynamic simulations, one for a spoiler angle of 0 deg and the other for the same spoiler declined at 30 deg. The results showed a considerable increase in downforce, but only a slight ...
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### Determining thrust equations for a custom UAV

I have been tasked to mathematically model and simulate a 2 propeller, 2 motor UAV. But I am struggling with determining the thrust equations, of the propeller, for my design. I know that: Ft = Ct * ...
76 views

### Max Lift to drag ratio

I have a question that I can't solve. Coefficient of drag= x, Coefficient of Lift= y, it is given that x= 0.015 + 0.05*(y^2), FInd Max Lift to drag ratio and I know that Lift to drag ratio is L/D= ...
89 views

### Fan starts making noise and air flow is reduced considerably

Yeah.. I dont know if this belongs here, I coulnd´t find a proper stack exhange site for this but it sort of involves physics I guess so... yeah. Basically, I have a ventilator, that after a few mins ...
114 views

### Why do (some) high-speed trains have curved (convex) walls?

Comparing the cross-section of modern high-speed trains to old train waggons, which had straight walls and were limited to speeds around 200 km/h, I notice that most of them have curved outer walls. ...
112 views

### Will the airflow inside a vacuum hose keep a sphere centered inside of it?

Suppose you were to fasten a string to a ping pong ball, then fasten the string to a stationary object, and then use a vacuum cleaner with a strong vacuum to suck the ball partially into the vacuum ...
29 views

### What is the cycle of simulation editing?

So this is very general, but... How are simulations for vehicles done? I know that computational fluid dynamic simulations are used, but why are repeated tests of actual hardware done too? Obviously ...
119 views

### Why there are no jets (missile or aircraft) faster than Mach 3.3?

Fastest plane ever built: SR-71 ,Max Speed: 3.3 Mach , Development - 1950s Fastest drone ever built: Lockheed-D21 ,Max Speed: 3.3 Mach, Development -1960s Fastest cruise missile ever built: Brahmos ,...
61 views

### Is it possible to generate energy from indoor draft by opening windows on opposite sides of the building?

Wind flow always generates naturally when I opening windows on the opposite sides of the building. Is it possible to put turbine on the way and generate electricity from that? It could be optimising ...
99 views

### Why don't propeller designers use multiple profiles?

I'm designing a ducted fan, and I'm deciding on the airfoil profile. NACA 16-series profiles are well-suited to M > .5 or .6, but they're not particularly efficient at lower Mach numbers. On the other ...
91 views

### RC drone rotor air access

I am attempting to design a "flying saucer." The saucer is an ellipsoidal-ish body with a RC drone inside. I plan to allow for air access to the rotors as shown in the rudimentary diagram below: I am ...
75 views

### How can i calculate drag on an Angled area?

I want to calculate drag force at special angle on a sphere . There are some grooves on the sphere and these groove have a special angle on the sphere. In other words, I want to calculate drag force ...
303 views

### ENLIL road-side vertical turbine - creating drag?

A company called Devecitech has just created what it calls the 'ENLIL' vertical axis wind turbine, that sits at the side of a highway generating electricity from the wind-power created by passing cars ...
67 views

### Will a fan that is composed of several fans fixed inside rotating tube work?

I want to design a custom 3D printed fan that would be made of several axial fans that would be connected (fixed) to their cylindrical casing. I am planning to rotate the whole assembly (the cylinder ...
57 views

### Heating the air inside a turbojet instead of combusting it

Would an aircraft that uses propellers for movement but with a turbo jet like structure where the ignition chamber only heats the air a bit, similar to a hair dryer instead of releasing fuel and ...
175 views

### Compressing the air thrusted by an aircraft's propeller through a cone like tube

If I had an aircraft that used propellers for movement and took the air from the front running it through a tube that gets very small towards the end, would it have any impact on the speed? Would the ...
462 views

### Formula for “ram rise” that works all the way to orbit

True Airspeed (TAS) is the vehicle speed relative to the surrounding air. My assumption is that if I am in orbit say at 120 km altitude with an instantaneous velocity of 8 km/s my TAS would be fairly ...
87 views

### Is it possible to extract mechanical energy using Turbines behind PulseJet engine?

Pulsejet expels pulse of hot gas (unlike turbojet engine) which create some thrust(Not good enough for ). These gases are hot, fast and pulsed. Is it possible to convert kinetic energy of these gases ...
2k views

### What is the optimal streamlined shape?

We all know the typical streamline shape which looks like a tear. But what is the optimum shape (for speeds 0-200 km/h)? Is the front a half sphere or is it an ovoid? How are the sides and the end ...
127 views

3k views

### Why use non-dimensional coefficients?

Aerospace engineering textbooks make frequent use of non-dimensional coefficients like $C_L$, $C_D$ and a whole host of others. Usually, for equations of motion, it is preferred to replace variables ...
3k views

### How to scale airfoil coordinates to achieve the required size?

I'm using airfoil data that is generated by a program. The generated airfoil has a chord length of 1 unit. I want to know how to scale up this airfoil to required chord length. My airfoil series ...
2k views

### Why do some high speed trains have long noses, while others do not?

Why do some high speed trains like the Shinkansen E5 and E6, have really long noses while other trains, like the Eurostar and Javelin, have shorter noses? How does the shape of the nose affect the ...
31 views

### Vertical wind measurements

How can the vertical wind direction be measured? For a project I have to design a wind turbine and I would like the blades to make slight adjustments based on the wind direction in order to achieve ...
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### Do all airfoils have a lift curve slope of $2\pi$?

I know that according to the thin airfoil theory all airfoils (symmetric or not) have lift curve slope of $2\pi$. I also know that finite wings should have less inclined lift curve because of the ...
205 views

### Questions about helicopter rotors - conservation of angular momentum

I have two basic questions about helicopters. Let's say the z-axis is the vertical axis from ground to sky. I know the tail rotor is there to counteract the angular momentum effects of the main rotor, ...
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### Air velocity through a tunnel 5,000 feet long and 30 feet in diameter?

I am an architect in need help with an aerodynamics problem for a design that I am developing. I need to know the the potential velocity of air moving from one end of a pipe to the other if any ...