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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How can centerline stagnation streamlines exist?
A stagnation streamline is a streamline that ends on the surface of an object, resulting in a stagnation point. Consider now the stagnation streamline for a symmetric object, which is along the ...
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Is there a difference in a water rocket's altitude based on the number of wings attached?
Let's assume for example, I have a water rocket with 4 wings, 90 degree angle between each one. In comparison to a rocket with 3 wings and 120 degree angles between each one.
Let's also assume that ...
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What causes drag crisis?
While reading the Wikipedia article on Drag Crisis, I found:
The drag crisis is associated with a transition from laminar to
turbulent boundary layer flow adjacent to the object.
While, the ...
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Forces On Toroidal Wind Tunnel wihen Wing is attached inside? [closed]
Consider the attached Toroidal wind Tunnel.
The Wind tunnel is in Vacuum and the moving air and the attached wing are only inside the toroidal tunnel.
Will the mounted wing on the walls of the tunnel ...
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Lift and drag forces in parachuting
EDIT: guys, I am not a physicist and it is not my study field, So even if you see my question is silly to be answered, I hope you can give me a clue.
I hope you are doing well.
I have some questions, ...
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Is There a Field for the Overlap of Geometry and Physics? [closed]
What I mean is how the shape of an object affects it's physical properties.
I've been studying Marine Biology and there's constant talk of how a fish's shape determines how well it can swim but no ...
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Showing that the integral giving the total induced drag exists
In John Anderson's Fundamentals of Aerodynamics the following expression for the total induced drag is given on page 442
$$D_i = \rho_\infty V_\infty \int_{-\frac{b}{2}}^{\frac{b}{2}}\Gamma(y)\alpha_i(...
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Why friction increase subsonic speed through pipe?
I know equations of Fanno flow but can anyone explain physically how friction increases subsonic velocity and decreases supersonic velocity through pipe ? is that for sake of boundary layer ...
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Propeller design comparison [closed]
Why does boat/airplane propellers are designed so differently then of a turbine/pump propellers? (blade spacing, pitch, blade shape and width, etc) although both just push fluids backwards
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Derivation of the Mach number of the reflected shock in shock tube
I am a new learner in compressible aerodynamics. When studying the shock tube, I struggle to derive the relationship between $M_{s}$ and $M_{R}$ after the shock is reflected from the end wall. How ...
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How to calculate the drag of inclined object?
For example, we have inclined flat panel in the plane that is parallel to the wind:
We can split the velocity into V1 = V * sin(α) and V2=V * cos(α)
then calculate two Re numbers and two Cd ...
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Does a cast net close as it descends or maintain shape?
There has been a bit of conjecture that fishermen's cast net closes gradually as it descends into the water column on the way to the bottom. My way of thinking is that a parachute stays open, despite ...
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How to calculate pressure change at a U bend of a rectangular duct, with a compressible fluid?
This is not homework, just a home project that I'm working on - although I'd like to get to the end result myself.
I'm familiar with Bernoulli's and Navier-stokes equations, it's just been a while and ...
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What should the linear velocity of an airfoil be relative to, when analyzing rotation?
I'm trying to figure out a free body diagram for this answer about why a parafoil-type parachute stalls easier at higher altitudes.
Question: If velocity (and therefore momentum) is always relative, ...
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How can you tell that the aerofoil has an asymmetric section only by looking at Lift to drag ratio against AOA?
I am new to aeronautics and I am interested to know how can the section of an aerofoil be determined just by looking at its lift-to-drag ratio against angle of attack ( $C_l/C_d$ as a function of AOA)....
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How can I estimate the drag of a CAD model?
I have a CAD model that I’m trying to optimize for hydrodynamic-ness, programmatically (preferably with Python).
Is there a way I can find or estimate the drag force of the model, without having the ...
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Understanding the physics of a vertical axis wind turbine
I have a physics background, but not much aerospace. I'm attempting to understand the operating principal of a vertical axis wind turbine. I've found a paper with a free body diagram, which I mostly ...
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Help calculating ideal power required for hovering [closed]
Suppose you had a system consisting of a large propeller and engine. In this scenario, the total weight of the apparatus is $160\hspace{1mm}\text{kg}$ and the length of a single propeller blade is $80\...
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Intuitive explantion of acoustic edge scattering?
Commonly the phenomena of leading edge noise is explained by the fact that disturbances in the flow scatter as sound. In the figure from Chapter 13 in Aeroacoustics of Low Mach Number Flows, at ...
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If an plane is in straight and level flight, is the rate of change of momentum of the surrounding air in the vertical direction equal to its weight?
Assuming that there are no effects due to atmospheric stability, it seems evident that a plane would impart downward momentum to the surrounding air at a rate equal to its weight. Is this true? I ...
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Where does the peak pressure increase due to an aircraft flying overhead reach the ground?
Is the center of the pressure increase at the ground directly under the airplane?
I have read in multiple sources that it is and there are arguments to support that. However one might also expect the ...
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Is it true that half of an aircraft wing's lift comes from upwash in front of the wing?
Something I read lately stated that the lift on a wing is due to upwash in front and downwash behind, each contributing equally to the air momentum change that results in the lift. If this is true, I ...
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Change in the Form of the Equation of Continuity with an increase in Turbulence
Up until now, my learning has mostly been restricted to laminar (streamlined) flow, and its equations.
One such equation is the equation of continuity (A1V1=A2V2). I was wondering whether, with an ...
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A shock propagates in to stationary air at $M$. Find the speed of the air (fixed frame reference) after the shock has passed
The speed of sound prior to completion of the shock is $M_1 * a$, where a is the speed of sound at that point.
The solution is then that the speed of the air after the shock has propagated is $(M_1 * ...
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CFD Boundary condition: Pressure far field vs Pressure outlet
I’m confused about a Pressure far field and Pressure outlet boundary condition
Should I be using a pressure far field (for the ‘outlet’ of the computational grid) instead of pressure outlet?
Flow is ...
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Unusual vortex actions along vehicle roof
Let me open by stating that I do understand the ethical implications of my failure to brush the snow off my roof.
After arriving at work I noticed an unusual snow erosion pattern on the roof of my car....
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Streamwise Pressure Gradient and Curved Walls
Could someone help me to understand how can a wall generate differents streamwise pressure gradients just by it's curvature? I can understand how it works in cross-flow (perpendicular to the ...
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Momentum Conservation in Lighthill Acoustic Analogy
I have a question of Lighthill Acoustic Analogy. In his paper, the approximate equation of momentum is
$$\frac{\partial}{\partial t} (\rho v_i) + a_0^2 \frac{\partial \rho}{\partial x_i} = 0 $$
Would ...
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Pushing air downwards using a fan, to hover in air
I believe that I am simply missing something over here, but cannot find it.
I want to just think theoretically, that if I use a fan (drone manner) to push air downwards, like a rocket, I would be ...
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What happens with the tip vortices of two aircraft flying in the opposite direction?
Suppose that an aircraft flies with its wing through an tip vortex of another aircraft which flew in the opposite direction. Suppose that the shed wing tip vortex of both aircraft are exactly the same ...
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Airflow through tube
I have a tube with an inline fan moving 100 cfm (cubic feet per minute). If I add an additional fan in the same tube capable of moving 100 cfm, what would happen? Would I increase my cfm to 200? Would ...
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PI controller - output calculation [closed]
The propeller of an airship is connected to a DC motor. The motor is being controlled using a PI controller. The PI controller has a proportional gain of Kp = 2, and an integral gain of Ki = 0.5, and ...
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What Continued Upwards Momentum Has to Do with Vortex in Bee Wings?
In this answer to how bumblebees fly, it says that
The wing motion has a sort of double lift feature. By twisting her wings over at the end of each down stroke, the upward momentum is never lost. ...
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How distance affect wind speed from a fan?
I noticed that when you feel the wind force from a fan close up, it feels like more force than from far away. Can someone give me an equation, where given a base wind speed $v$ in mph of the fan, and ...
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Glider in kite mode - what main parameters to expect?
I need to use the device similar to glider in kite mode.
So it will be attached to some load that will be attached to the ground.
It should work in usual wind speeds like 5 ~ 10 meters per second.
...
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How to find equilibrium rpm of a wind-turbine / free-spinning rotor (using BEM)?
Background: I want to design a rotor-recovery system, which uses a free-spinning rotor to slow a fall instead of a parachute for example. From a mechanics and aerodynamic standpoint it should work ...
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Attempting to Model Air Resistance in Javelin Flight
I am trying to do a mathematical modelling project on javelin flight and correlate the data to real life data from the Olympics. Obviously, drag is an important component of the flight characteristics....
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Is This Derivation of Velocity as a Function of the Force of Air Resistance Correct? [closed]
I have seen the derivation of velocity with air resistance done using the equation, $F_d=-bv$ where velocity can be expressed as
$$v(t)=v_0e^{-\frac{b}{m}t}.$$
However, I'm looking for a corresponding ...
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How is the damping coefficient $b$ calculated for the air resistance for a sphere (horizontal motion)?
The derivation of velocity which takes air resistance into account takes the form:
$$v=v_0e^{-\frac{b}{m}t}$$
which is derived from $F_D=-bv\implies a=\frac{F_D}{m}=-\frac{bv}{m}$. I heard that the ...
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Is it possible to convert separated flow back to attached?
Sometimes you cannot easily create ideal single streamlined shape...
Would it be possible to attach separated flow again somehow?
The point is - you have some base setup (average cyclist) and want to ...
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Is the density of air inflow at room condition the same as stagnation density in a combustion chamber of a rocket system
We know that the density of air doesn't change for air speed very less than mach one at the nozzle, and the stagnation density is the density at zero air speed. my question is, does this mean that the ...
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Would Aeroplanes or Helicopters work on our Moon?
Would Aeroplanes or Helicopters work on our Moon?
In general , I think , in Aeroplane Case:
(1) Air is required for Aeroplanes to float : Would Moon have enough air?
(2) High speed is required for ...
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Does Kelvin's Circulation Theory apply to Aerodynamics?
Circulation is used widely in the aerodynamics textbooks as a way to explain Lift.
It invokes Maxwell’s Circulation Theory and is summed up in the following figure 4.21 from Anderson’s Fundamentals of ...
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Does a fluid with the same static pressure exert different pressures at different velocities?
Let's say there are 2 identical pipes (same diameter, surface roughness) in which a fluid flows.
The static pressure of both the flows are equal. But Flow A is faster than Flow B.
Will there be any ...
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How does drag change at very low gas density?
The usual expression for the drag force $F_d$ of an object with velocity $v$, cross-sectional area $A$, and drag coefficient $c_d$ is
$$F_D=\frac{1}{2}\rho v^2 A c_d$$
where $\rho$ is the density of ...
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How do aerostatic machines work?
so i was wondering how aerostatic machines work? So do they actually use the surrounding air to take off?
And how is aerodynamics the ‘opposite’ to this?
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How do you calculate velocity reduction over time due to drag, when drag is also a function of velocity?
The drag equation is: $F_D=\frac12 \rho C_d A v^2$, assuming constant values let's simplify to $F_D=Cv^2$
Assuming there are no other forces to consider, I'm really not sure where to go from here. I ...
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What boundary conditions are used to CFD simulate airflow over an aerofoil?
As I understand it, in CFD, a boundary is the geometrical surface around the system where you define the starting conditions for the simulation: For the analysis of fluid flow through a pipe a pipe ...
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Energy balance in fixed wing flight, action/reaction
When an airplane is in flight the engine of the plane overcomes drag until the plane is moving forward fast enough to balance drag. In a stable configuration the air moving over the wings creates lift ...
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Have any experiments been performed on how to maximize atmospheric drag on a surface?
While looking for any research on maximizing drag, all of my searches produce studies on how to minimize drag. Is anyone aware of experiments performed to maximize drag on a surface? Is it even ...
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