Questions tagged [drag]
The force on a body resulting from it's motion through a fluid (gas or liquid). This force is directly opposed to the direction of travel.
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Signum function and friction
There've been some times where I've seen people including the signum function, $\text{sgn}(v_x)$ in equations of motion to account for the instant when the horitzontal velocity component, $v_x$, ...
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Why Is Wind Energy Velocity Cubed Instead of Squared?
Formula for everything seems to be squared, for example, kinetic energy $KE = \frac{1}{2}mv^2$
But for wind energy, this formula is cubed, e.g. $\frac{1}{2}\rho A v^3$
I couldn't find any results for ...
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Drag coefficient of an oscillating film in a turbulent flow regime (stirred tank), experiment or theoretical?
I have been recently assigned to a new project and brushing up my fluid mechanics from years ago, so sorry if the question is too stupid to post here.
The goal is to quantitatively measure some form ...
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Complex shape drag coefficient
Is there theoretical way to compare drag coefficient of complex shapes without full CFD simulation ?
For example which of these shape have or could have best drag coefficient or could any be improved ...
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How do I rigorously prove that a ball dropped straight down doesn't move sideways (with quadratic air resistance)? [migrated]
Consider a 2D problem in which I drop a baseball straight down from some height. In this regime, one can show that the dominant contribution to the drag is a quadratic dependence directed opposite the ...
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Air resistance in the Cavendish Experiment
Would air resistance be an issue in the Cavendish experiment or are the velocities so low as to be irrelevant? Could it cause the experiment to fail?
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In beer, why do bubbles travel faster upwards in the center?
This is a very odd question, but I just so happened to be observing a pint of beer and realized that the bubbles floating up seemed to travel faster towards the center of the glass than towards the ...
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Why doesn't the ratio of inertial to viscous forces ($R_e$) depend on the object shape - frontal vs side area?
Why doesn't $R_e$ depend on frontal and side area? - Understanding Reynolds number in the context of varying object geometries.
I have not taken a fluid dynamics course, but have been reading up on ...
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Graph of acceleration against time?
Considering no air resistance, the acceleration time graph for a free falling object would be a horizontal line as the acceleration remains unchanged. When we do take into account air resistance, the ...
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Frictional drag coefficient for flat plate normal to a uniform flow
In the case of a flat plate perpendicular to a uniform flow, it is commonly understood that for high Reynolds numbers, the drag coefficient ($C_D$) is known to be around 2.0. While many references in ...
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Why does a hemisphere facing into oncoming fluid fare slightly better than a wedge?
I saw this graphic on Wikipedia giving the drag coefficient of a variety of shapes placed into an oncoming fluid medium:
https://en.wikipedia.org/wiki/Drag_coefficient#/media/File:...
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The solution of linear air drag and transcendental number $e$
I was watching a course about classical mechanics and in the chapter on air resistance the instructor wanted to show how transcendental numbers appear to the solution of linear air drag differential ...
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Numerical Method for solving Newtonian Equation of Motion for Particle experiencing drag in fluid flow
Currently, I have a fluid solver that can calculate the lift and drag forces acting on a body on a per timestep basis. This means that I have data regarding the hydrodynamic forces only for the ...
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Why does the angle for maximum range decrease in the presence of drag?
In the absence of drag, the angle to launch a projectile is 45°. In the presence of drag, the angle to attain max range is complicated. However, there seems to be consensus that it has to be less than ...
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How is the Reynolds number derived(my derivation is wrong)?
I'm a HS student so please dumb it down.
I'm looking into the Reynolds number of a sphere sinking in a fluid, here's what I got.
Inertial drag force = 0.5 * 0.47(CoefficientOfDragSphere) * rho(...
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Vertical Projectile with linear air drag
If a spherical ball of mass $m$ is thrown upwards with an initial velocity $v_0$ and it experiences linear drag, how do we come up with expressions for $v(t)$ using Newton's second law (taking up as ...
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Friction over a rotating ball under water
What's the friction force over a rotating ball under the water (or any other fluid)? The center of the ball is at rest, so I'm only interested in the slowing down of the rotation of the ball.
My first ...
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Settling velocity of a particle in a Bingham fluid
I am trying to calculate the settling rates of a particle (xenolith) in magma in order to infer the magma ascent velocity. Assuming the fluid is Newtonian, this can simply be worked out using Stokes ...
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Are meteors heated primarily through radiation or convection (or both)?
From what I read meteors compress the air in front of them, increasing the air's temperature massively; this in turn is what heats the meteor. My question, which I can't seem to find a clear answer to ...
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Does the Earth experience air resistance?
Consider the earth body excluding the atmosphere, undergoing circular motion around the sun. Does it experience air resistance due to the atmosphere?
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How does length effect drag?
Section of pipe: 20mm diameter, 2000mm length, hemisphere end cap. Moving horizontally through water, I think that the coefficient of drag would be approx. 0.42.
How would the length of the pipe ...
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Optimum baseball distance from velocity
I am trying to come up with an equation that is able to approximate the magnitude of velocity of a baseball after it travelled a certain distance in the $x-$direction given the ball is thrown at an ...
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Unreasonable values obtained for a simplified helicopter in equilibrium
I'm attempting to analyse a simple model of a helicopter. For one of my equations, I'm summing the forces in the x direction (forward motion). There are only really two forces acting on the helicopter,...
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Would an adhesive surface have more air resistance?
Imagine spreading double-sticky tape all over the surface of a car or a plane. Would there more significantly more aerodynamic drag as a result of the adhesive 'sticking' to air molecules and slowing ...
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Shooting a bullet in motion
If a bullet is shot from a firearm from a moving car in the direction of movement, would the speed gained with respect to the car be same as the speed of a bullet that is shot from an immobile gun?
I’...
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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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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 the sensation of falling purely due to air resistance?
When I jump off of something, even with eyes closed I can be pretty certain that I'm falling due to the associated sensation of falling. However, as gravity should be affecting each of my internal ...
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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 is it faster to swim under water than on the surface?
In competitive swimming, swimmers are allowed to swim first 15 meters completely submerged, and it seems that they can swim much faster that way than if they swim on the surface.
I've seen several ...
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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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Need help solving a projectile motion problem: finding the angle for a thrown ball to intersect with a vertically falling ball
The problem states that a ball is dropped from rest and falls under the influence of gravity (neglecting air resistance). At the same time, another ball is thrown with an initial velocity of v0 from a ...
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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 decompose Plasma ion Drag Force on a particle moving through it?
Almost all papers on plasma mentioned that plasma ions drag on a particle is in the direction is opposite to the velocity of the particle. But no one said anything about the other two components; are ...
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What are the Components of drag force in spherical polar coordinates? [closed]
How to decompose the drag force in three components of spherical polar coordinates?
Since
$ F =\frac{1}{2}\rho C A v^2 $
or in vector form :
$\vec F = \vert F\vert \hat F = \frac{1}{2}\rho C A v^2 \...
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Effect of apex vent on reference area in equation for drag coefficient
I am trying to investigate the effect of apex vent (vent ratio) on the drag coefficient of circular parachutes, via a drop test using scaled down parachutes. How do I determine the reference area of ...
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Cyclist coasting on a plane road (only air resistance and rolling resistance apply)
I am currently trying to simulate a cyclist. Right now I am looking at the change of velocity when the cyclist is coasting on a plane road. These are the values I am using:
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Air resistance in two dimensions
Suppose I have a ball moving through the air parallel to the ground, and diagonally in some 2D $x$ , $y$ coordinates (along the line $y=x$). Let's say its velocity is 1 units, which means on the $x$ ...
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Power consumption / energy expenditure to maintain constant velocity while riding a bicycle at $1\times$ velocity vs $2\times$ velocity
Consider the case of someone riding a bicycle on an even horizontal surface at a constant velocity. As they are riding at a constant velocity, there is presumably a constant energy expenditure (which ...
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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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Integrating both sides of an equation w.r.t. two different variables ($dz$ and $dv$)
so I'm trying to derive an equation for the maximum height an object reaches after being vertically thrown upwards, where the two forces acting on it are gravity and quadratic air resistance, so that
$...
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Why is a viscous drag produced due to relative motion of layers of fluids? [closed]
When two layers of fluids move over each other, a viscous drag is produced. Could you please elaborate on this?
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Is air drag approximately the same on both a smooth ball and a tennis ball?
I am writing a project about projectile motion in 2D at a high school level to the point where I only know the simple drag equation. The experiment I did was firing a tennis ball with a compressed ...
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Regarding Speed of launched rocket inside the atmosphere
I am a 15 yr old, so please forgive my mistakes as I have not entirely read rocket mechanics.
I have been wondering why rockets accelerate to mind-boggling speeds, (mach7-8 or even more)when that must ...
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Can the damping coefficient of a pendulum be predicted given physical variables?
I'm aware you're able to calculate the coefficient of damping, $b$, given a set of amplitudes over time through $$\ln(\theta/\theta_0) = -bt/2$$ However, is there any way to get $b$ without empirical ...
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Drag force on a bicyclist
Recently, I wrote an introductory physics exam where I encountered the following problem:
We look at a bicyclist with the wind drag force $\vec{F_R}(t) = -k \vec{v}(t) |\vec{v}(t)|$ who accelerates ...
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Husband and Wife with Metal and Fabric Parachutes [closed]
Let's suppose: an open parachute made of fabric with a lady hanging below, starting from stand still, falls from 5000 meters. Another parachute made of thick metal, with the same size and shape as the ...
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Speed of objects travelling down liquid-filled tubes of different widths
Consider I have two tubes filled with water: Tube A and Tube B. Tube A has a diameter of 20mm and Tube B has a diameter of 10mm. A marble ball with a diameter 8mm is dropped down both tubes.
Why does ...
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How damping constant of pendulum varies with length of wire? (experiment result confusion)
I'm a high school student doing an experiment for my physics course. The experiment aims to find out the relationship between the damping constant and the length of the wire. The constant is ...
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