Questions tagged [aerodynamics]

A subset of the [fluid-dynamics] tag concerning primarily forces such as lift and drag generated on bodies as they move through gasses or as gasses move through the body (typically air).

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Aeroacoustics Simulation in Star CCM+ using FW-H Model

Trying to simulate the aeroacoustics noise generation due to a flow over an open cavity using Broadband Noise Model and also noise propagation in the far field using FW-H Model. The Star CCM+ user ...
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6answers
115 views

Origin of the thrust force in jet engine

I am reading a lot about the jet engine operation and I meet mostly explenation that the thrust is generated thanks to the exhaust nozzle that "accelerates" the air. However the nozzle ...
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Calculating soar uplift

As I understand it via https://en.wikipedia.org/wiki/Lift_(soaring)#Thermals some birds and gliders use warm columns of air to provide lift and stay aloft without an onboard engine. I would like to ...
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Why is there an "unsinkable disk" phenomenon? Is it related to the lift of the aircraft?

A metal disk with a hole at its centre sinks in a container filled with water. When a vertical water jet hits the centre of the disc, it may float on the water surface. Explain this phenomenon and ...
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1answer
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Why cant there be a sonic velocity inside the convergent part of a nozzle? (ie upstream of the throat)

A convergent-divergent nozzle is typically used for accelerating or decelerating airflow to or from supersonic speeds. The typical configuration for such a nozzle is the de Laval nozzle that is ...
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5answers
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Why don't bullets used in guns have sharp corner edges? [closed]

Why don't bullets used in guns have sharp corner edges? Like why are they spherical or smooth at the tip? Is it to avoid air resistance? But as my sir told that how speed we move proportional we get ...
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1answer
25 views

Pitot tube airflow speed measurement

how pitot tube can specify the airflow at aircrafts. according to formula airflow speed is related with fluid density. when aircraft passes through clouds it meets different density of fluid than ...
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3answers
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Can astronauts fly like birds in the space station?

Can astronauts fly like birds in the space station? The space station is microgravity, and astronauts can't walk. Can we design a pair of wings for astronauts to fly in the space station? What if the ...
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4answers
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Slipstreaming - is there a penalty?

When a following vehicle slipstreams close to a vehicle in front, by placing itself in a region of air moving at a similar velocity to the front vehicle, it is afforded a benefit, e.g. improved fuel ...
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How exactly does a fixed pitch wind turbine start from standstill/stall?

I might have a crucial gap in my understanding of the aerodynamics of a wind turbine but I am struggling to get my head around how a fixed pitch wind turbine can start spinning from a standstill? I ...
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1answer
72 views

Why does a crumpled paper fall down faster than a flat paper? [duplicate]

It can't be because of less surface area as we know that friction is independent of the surface area
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Aerodynamic Problem in regards to a ping pong ball and and an open hole tube

I have a ping pong levitation system with a ping pong ball in a tube being pushed by a dc motor fan (shown below) and I'd like to define a relation of the balls height with the air velocity or airflow....
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Why d'Alembert's paradox has zero drag?

Why d'Alembert's paradox has zero drag? Even if viscosity is zero why drag is zero if there is no stagnation pressure at the back (right) side of ball? Why flow stay attached to ball surface,even ...
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4answers
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Can the UAV fly in the space station? Can birds also fly in the space station?

Can the UAV fly in the space station? Can birds also fly in the space station? Birds can bump around the space station.
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1answer
39 views

Treatment of the Damping term in pendulum equation [closed]

I am confronted by two differing equations for a damped pendulum. I want to back out the drag coefficient at each point of a pendulum's motion. I have the velocity and the acceleration at each point. ...
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How to calculate the wind load force value and direction for the round cylinder tilted downwind?

I tried to look in internet but I mostly find the wind load on flat surfaces and square cylinders. In fact I need to determine the angle of the helium filled round cylinder attached to the ground so I ...
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1answer
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Predicting drag or drag coefficient?

Would it be possible to mathematically predict what the drag on free-falling object will be in 10 seconds (for example), if you know the current altitude, velocity and pressure? I know you can ...
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1answer
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What is the physics principle behind Helicone (wood toy)?

There is kind of toy "Helicone" (https://www.youtube.com/watch?v=nkmBLPHGp0E), It is composited with one base, one axle and many co-axle leaf-pairs. When rotating it in a direction and ...
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1answer
74 views

Do heavier cyclists experience relatively less wind resistance?

I am a cyclist with no physics training (beyond high school). In general, lighter cyclists with high power-to-weight ratios are the fastest, but I am wondering if there is an advantage to being ...
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How does Venturi effect work in this case?

I'm not a physicist or a student. I just wanted to understand how the Venturi effect works in this case. I understand that the Venturi effect says that when a fluid flows through a constricted area, ...
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0answers
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Flight distance of light bullet vs heavy bullet

The Problem We have argued with the brother, whether the heavier of lighter bullet will fly further. Intuitively, the lighter bullet has more velocity $v$ and can cover more distance before it falls ...
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2answers
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Good, modern books on aerodynamics

I graduated in Aerospace Engineering years ago, and I work in a completely different sector now. However, I would like to get a modern book on the topic and see how it's taught today. I understand ...
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2answers
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How do flat insect wings generate lift?

The traditional Bernoulli explanation of lift depends thoroughly upon a wing which, through differing geometry between the upper and lower wing surfaces, causes higher air velocity above and below, ...
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2answers
274 views

Relative efficiency of airplanes and helicopters, why is this argument wrong?

I'm trying to better understand why helicopters are less fuel efficient per unit distance than airplanes. One argument I keep seeing in other questions on the topic is that helicopters actively ...
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4answers
3k views

Why do all fighter jets and aerobatic airplanes have flat wings?

According to Bernoulli's principle and for a given angle of attack would that not lower the lift force of the airplane and increase its drag and therefore increasing its demand in thrust and fuel ...
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2answers
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How are shockwaves created if no particle goes around the wings at supersonic speed?

so,the title could be a bit misleading, let me elaborate: whenever studying aerodynamics, the explanation starts with considering the wing of a plane still, and the flow of air arriving from either ...
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1answer
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Difference in energy required between flying Verically vs flying in the same horizontal plane

An insect of mass 150mg is hovering. What would be the energy required to fly straight up 10cm (against gravitational force) vs forward 10cm? Weight of insect:150mg Displacement:10cm I want to know ...
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1answer
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Direction of supersonic shockwave on a bullet with lateral velocity

When a bullet travels at supersonic speeds, it generates a shock-wave. For a bullet traveling in a straight path, the shock-wave is oriented in the same direction as the bullet. But if a bullet is ...
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Why is wingsuit water landing without opening a parachute not a survivable event?

According to this YT video, just before this wingsuit flyer opened his parachute his speed was below 90 KPH. When you jump off a 100 foot cliff your impact velocity is around 87 KPH and people have ...
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Why jet of air can follow so much curvature?

In normal condition(aircraft in flight or aircraft in wind tunnel) if wing has so much curvature like coanda ball has(picture below),air will detached from surface.. 1.Why jet of air stay attached to ...
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Which object has lower drag? [duplicate]

Two same objects,only difference are parts that are paint in red,5m long,fluid air,veloctiy up to 300km/h. Which object has lower drag of these two and why(explanation)?
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2answers
91 views

Has car round back any aero advantages? [closed]

All Porsches have round back so much(top to down and also side to back) that people know to joke that car has lower drag when drive in reverse! Does so much round back has any aerodynamics advantages ...
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1answer
167 views

Why car has sharp separation edges at the back?

Most new cars that gain low drag have sharp separation edges at the back. If edges are round than wake is smaller but curvature produce low pressure, if edges are sharp wake is larger but dont have ...
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1answer
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Why does the pressure drop behind a windmill actuator disk?

The canonical derivation of Betz's law for wind turbines discusses pressure before and after a windmill actuator disk. It's obvious that the wind resistance of the disk would cause a pressure increase ...
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To what extent can atoms be *specularly* reflected (in the context of high velocities in a rarified atmosphere)?

This is a follow up to earlier comments below this answer regarding orbits at low altitude. The suggestion is to try to obtain energy from the Earth's rotation to maintain an orbit with a very low ...
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1answer
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Would a rotating sphere placed within a pipe with air flowing through it experience a lifting force due to the Magnus Effect?

I am wondering if a rotating sphere placed with a pipe/duct with air flowing through the pipe will cause the rotating sphere to experience a lifting force due to the Magnus Effect. Moreover, if the ...
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1answer
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Newtons third law explained on an airfoil at a molecular level

I understand there are many different ways to explain lift on an airfoil, one of which is flow turning, that being due to the coanda effect on the upper surface of the airfoil, it deflects incoming ...
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Bernoulli Equation Normal to the Streamline

Good Evening, I'm thinking about the expression of the Bernoulli Principle in the tangential and normal directions of a StreamLine. A. Along the streamline : $$\gamma z \ + p \ + \frac{1}{2} \rho v^2 \...
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Consideration about Bernoulli Theorem

I was considerating the Bernoulli Statement about the fact that in a Stationary and Inviscid Flow an increase in the speed of a fluid particle correspond to a decrease in its static pressure. I'm ...
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1answer
3k views

Why is an airfoil shaped like a teardrop?

I understand the reason airfoils are cambered on the top: to create lift. But one would assume this would result in aircraft wings having a semicircle-shaped design. Why is the cross-section of an ...
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Use a single function to express the relationship between spalding mass transfer (B) number of water droplet and relative humidity (RH)?

I'm totally inexperienced in fluid physics but I need to put spalding mass transfer number of water droplet and relative humidity into one function in my work. Through some research, I knew that $B=\...
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Optimal shape for air inlet with least disturbance

I aim to measure the atmospheric $\text{CO}_2$ concentration (also many greenhouse gases) of a city. The measurement will be made on a tower, at the height of $130$ m. I have a KNF diaphragm pump and $...
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3answers
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More confusion about the faster-than-wind Blackbird

There's been plenty of discussion on here about the Blackbird as featured in this video. I get that it harvests energy from the relative velocity of air to ground. But I still can't wrap my head ...
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The lift of an airplane is similar to that of a balloon. It uses the density difference of air, right?

The lift of an airplane is similar to that of a balloon. It uses the density difference of air, right? The air density on the top surface of the balloon is low and the air pressure is small. The air ...
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0answers
32 views

The reason behind fusion of jets

I was looking at jet planes flying in the sky and noticed their two jets seem to project in a diverging direction at the end of the engines, but they reunite later. I am posting two example ...
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0answers
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Impact of the location of the aircraft propeller on yawing moment

we know that the effect of P-factor on puller propellers is the yawing moment in the opposite direcrion. i mean if we had a load(thrust or lift) on the right side of propeller , then airplane will yaw ...
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1answer
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What is the nature behind the periodicity of the Mach diamonds?

I've heard very interesting and sometimes contradictory hypothesis about why the Mach Diamonds have well defined spatial periodicities. I am not sure I understand most of them, and I cannot exclude ...
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What if a skydiver hits another parachute?

So, hypothetical scenario: 2 Skydivers are falling, directly on top of and in close proximity to each other. The lower one opens his chute, while the upper one keeps falling. What happens? Does the ...
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1answer
52 views

How can we calculate $g$ force in this maneuver?

How can we calculate $g$ force in this maneuver? We are not dealing with conventional maneuvers like level turn or loop so what equation used to calculate g force in this maneuver? What about other ...
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1answer
57 views

How does a propeller work?

I was thinking about the force that balances the force of gravity in a drone, and I stumbled upon this question that how to mathematically describe the upthrust being generated by the propeller, as a ...

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