Questions tagged [aerodynamics]

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461 views

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 * ...
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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= ...
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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 ...
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2answers
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. ...
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1answer
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 ...
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1answer
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 ...
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1answer
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 ,...
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2answers
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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 ...
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1answer
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 ...
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1answer
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 ...
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1answer
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 ...
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2answers
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 ...
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2answers
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 ...
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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 ...
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2answers
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 ...
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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 ...
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2answers
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 ...
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3answers
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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 ...
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1answer
127 views

Why does 3D source potential flow only satisfy Laplace's equation in spherical coordinates and not cylindrical coordinates?

3D source potential flow is given by: $\phi = \frac{-\lambda}{4\pi r}$. Laplace's equation in cylindrical coordinates is: $\frac{1}{r}\frac{\partial }{\partial r}\left(r \frac{\partial \phi}{\...
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1answer
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Scanning and modeling my personal vehicle for aerodynamic simulation

I have this pickup truck that I love dearly. I often change the aerodynamic configuration of the truck when I use my camper shell, or roof top tent, etc. Is there a reasonably easy way to create a ...
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1answer
61 views

Why do some cars have flow channels in their bodies to decrease drag?

From my understanding, the more surface area the flow passes, the more drag happens due to skin friction. An example of this is the new Ford GT, which has a converging cockpit and separated side body ...
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What is the theoretical relationship between sound and mass with respect to the sound barrier as a max velocity?

First post here, forgive me any faux-pas. In regards to compressible flow and accelerating a mass flow, such as in a converging nozzle, I know that you can't accelerate a mass past the speed of sound (...
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1answer
391 views

An Argument from Kelvin’s Circulation Theorem

Page No. 318, John Anderson’s “Fundamentals Of Aerodynamics”. The author here states from Kelvin’s circulation theorem that the initial circulation around a closed loop including the airfoil when the ...
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1answer
262 views

Proving Kelvin’s Circulation theorem

I’m following Anderson’s Fundamentals Of Aerodynamics. However, the proof for the above theorem is not provided. Every time I try it, things get really lengthy and cumbersome. Is there some nice and ...
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1answer
116 views

Propeller design

I see on internet, that aircraft propellers most effective blades angle only 15 degrees on every blade. Why propellers not use 45 degrees angle on propeller's blade that give more thrust on the ...
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1answer
167 views

Reducing air flow speed without much backpressure

I am setting up a test-bed for an experiment. Here's what I have. A circular car exhaust like this Image The gas comes out of the exhaust at a velocity, x. We need to lower the gas velocity to X/3 ...
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1answer
245 views

What's the slowest airflow speed a ramjet could work?

Thinking experiment about a flying device having the fewest moving parts, whats the slowest cruise speed achievable using a ramjet, no matter the scale of this device. Working altitude is troposphere. ...
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A Question of Coaxial Rotors and Lift

I'm only a HS physics student, so please bear with my lack of jargon. My question goes like this: In the scenario of two coaxial rotors spinning independently in two different directions, each with ...
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Determination of a Joukowski airfoil chord (demonstration)

I'm currently studying Aerodynamics, and one thing that I noticed is that the maximum and minimum $x$ coordinate of the airfoils (which are necessary to compute the chord) on the transformed plane (...
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3answers
2k views

Fluid dynamics right angle air duct

I am designing a printed piece that will deflect air from an exhaust fan on a computer 90 degrees. My question is, what would be most efficient, a circular radius, parabolic radius, or hyperbolic ...
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1k views

How to generate a NACA 6-Series Airfoil analytically?

I asked this question over at Aviation.stackexchange but after that I figured it might be better to place it here. Especially since there were really good answers on the NACA 5-digit-Series airfoil ...
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2answers
357 views

How can I generate smoke (or mist) that leaves no residue?

I have to visualize flow over some designs in my wind tunnel. However, my advisor has stated that previous students have wrecked the machine when they have used oils and I think Dry Ice might ...
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1answer
180 views

Ceiling or table fan better

I always wonder in directional flow which fan would send colder.air and cool better. I am biased toward table fan as it throws fresh air while ceiling fan throws stale hot air accumaled at top. Please ...
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1answer
108 views

Wind resistance inside turbulent flow (“prop wash”)

I have an object that is launched from the side of a plane (it is a flare). The question is: what does the flare do while it is proximate to the plane? Will it hit the tail? After accounting for ...
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4answers
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What does “tempered water” exactly mean and how does it help cool the air?

It's from Apple's latest Earth Day commerical called “Can a building breathe”. https://www.youtube.com/watch?v=tNzCrRmrtvE The commercial is about Apple's new naturally ventilated building called "...
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1answer
139 views

Wing as cantilever beam (beam-rod) model for aeroelasticity fluttering analysis

I recently bumbped into a rather basic but interesting question on aeroelasticity. I've learned to derive the fluttering critical speed from Pines's theory but it involves some spring stiffness like ...
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2answers
75 views

How heatseekers change their course?

Heatseeker when locked on target(say a jet), follows the target until the it is hit, what happens when target is moving and changing it's direction.how does the heatseeker it's changes direction at ...
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1answer
40 views

Finding Source of Heating Rate Equation

I am currently working on creating a tool to calculate the maximum heating rate on a re-entry vehicle given starting conditions and coefficients. I am using Re-Entry Aerodynamics by Wilbur L. Hankey ...
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2answers
52 views

Deceptional Pitot Tube

speed measured by pitot tubes is that of the wind speed relative to the aircrafts. Now, this itself depends on weather conditions which can affect wind speeds. So, then why employ pitot tubes at all ...
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what is the actual meaning, role and aim of $p_0$, $V_{a_0}$ and $V_c$ for Mach-meter?

Roskam, book "Airplane Aerodynamichs and Performance" at subparagraph: "2.5.2 HIGH-SPEED AIRSPEED INDICATORS (COMPRESSIBLE FLOW)" uses the following three equations: a) $\left(\frac{\gamma}{\gamma-1}\...
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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 ...
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2answers
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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 ...
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2answers
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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 ...
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1answer
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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1answer
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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 ...
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3answers
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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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1answer
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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 ...
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4answers
857 views

How does a stator convert velocity into pressure?

I'm looking for, hopefully, a qualitative answer to how a compressor increases pressure. I understand the equations that predict this result but I can't picture it in my head. A rotor spins, ...
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1answer
387 views

Hydrofoil for skeg-hung rudder with forward centre-of-effort

I am trying to see how much I can reduce the torque on a rudder post by changing the foil shape. I think I need a rudder with a centre-of-effort further ahead than average but I don't know what rudder ...