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Questions tagged [flow]

The motion of fluids (gases, liquids and granular material).

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15 views

Is it possible to equate the radius of a hole using poiseuille's law?

I want to calculate the radius of a hole from the leak rate. I have come across Poiseuille's law which includes the radius of pipe/hole. Is it possible to equate the radius of the hole from the volume ...
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Is Coefficient of viscosity frame dependent? Why/Why not?

Is Coefficient of viscosity frame dependent? Why/Why not?
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What are good textbooks or documents to learn numerical simulation about open channel flow like river flow?

I'm trying to learn about numerical simulation about river flow. The problem is I am a CFD beginner (just studied about hydraulics). So I don't know history or important topics about numerical ...
74 views

Why is the stress tensor simplifying like this

\begin{eqnarray} \nabla \cdot \boldsymbol \tau &=& 2 \mu \nabla \cdot \boldsymbol \varepsilon\\ &=& \mu \nabla \cdot \left( \nabla\mathbf{u} + (\nabla\mathbf{u}) ^\mathrm{T} \right)\\ &...
11 views

Maximum velocity of isentropic compression

In the isentropic compression tables, if P/Po = 0.9999, then A/A* = 57.8738. This is from the isentropic compression table found here: http://www.cchem.berkeley.edu/cbe150a/isentropic_flow.pdf Am I ...
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Finding the flow rate of a gaseous oxidizer flowing through a solid fuel (and they're combusting!)

I'm wondering, is there a way to calculate the volumetric flow rate or mass flow rate of oxygen flowing through a solid fuel (ex. paraffin wax) and combusting with it? After the combustion, the flow ...
3k views

Water Bottle Rocket Thrust - two calculation methods not matching

I have been launching water bottle rockets with my kids and we are in the process of creating a simulation of the launch using numerical methods. I am a mechanical engineer, but fluid dynamics is not ...
34 views

Air velocity from a 5mm pipe

At first, I will try to describe my problem. I have a compressed air at 0.4 MPa (4 bars) that goes trough a control valve and a flow meter into two 5 mm pipes. Flow meter shows the value of 200 ...
25 views

17 views

Flow velocity ambiguity in transition region

I have calculated the following short table concerning the stationary flow of water in a 1 meter long pipe with a diameter of 16 mm and a completely smooth inner surface. The flow is driven by the ...
15 views

$Gm/r$ in momentum equation of compressible flow for cylindrical geometry

In the case of compressible flow, due to the gravitational field, the source term added in the momentum equation (which is gravitational potential) is $Gm/r$ in the case of cylindrical geometry and \$...
28 views

Flow in bend pipe

What happens to a flow in a bent pipe of uniform cross sectional area? Will there be any change in flow velocity at the outlet? If yes, why does it happen? What happens at the bent area of the pipe? ...
4k views

What is the shape of the upper boundary of water hitting a screen?

When I saw that thing I did not understand how that shape is formed? To be ideal, take a vertical smooth plane. Now aim at the wall with a thin water tube. Then the outer layer forms a "parabolic ...
63 views

What is irrotational flow? How to judge?

For example, when the wing moves horizontally, the direction of fluid flow changes first to upward at the leading edge of the wing and then to downward at the trailing edge. Does it rotate? If the ...
31 views

calculate CFM of a ceiling fan

I'm trying to calculate, or even understand what data do i need to calculate the CFM of a ceiling fan. in many countries this is a given data in the product details but not where I'm from. I have the ...
17 views

Acoustics air flow vs the human body

My question to you all is... Is it possible to move air acoustically. ie to move air over a 2.1m distance to be felt by the human body with a cooling effect but not heard by the human ear ? I'm just ...
65 views

Problem estimating the flow rate in natural draft chimney using Bernoulli equation including heat and friction losses

I am trying to build a simple model for fluid flow and heat transfer in a natural draft chimney. I've found some literature about it (most of them giving the same result as the equations on the ...
49 views

Why does blood pressure drop when blood vessels rupture?

Some people say that because the flow is large, the pressure is low. Is that right? Why does the pressure drop when the flow rate is high?
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How to measure flow rate using Toricelli's law?

For my experiment, I want to investigate the relation between height and velocity using Torricelli's law. I would like to know how I would measure the flow rate from volume in a spouting cylinder.
62 views

Viscous losses in loop helical flow

Imagine flow of the following kind. The flow line for each flow particle is a helix with its axis bent so that the beginning attaches to the end. How can I determine the viscous losses in this flow ...
107 views

Do drones fly because of low pressure above them or high pressure below them?

I was working on some drone battery life solutions and was stuck with the question whether drones fly because of low pressure created above them by the rotor or due to high pressure created below them....