# Questions tagged [fluid-dynamics]

The quantitative study of how fluids (gases and liquids) move.

5,993 questions
Filter by
Sorted by
Tagged with
35 views

12 views

### How much power is needed to turn a water turbine in reverse if the power produced by the turbine in normal operation is known?

The picture below shows a farm of underwater turbines placed in a river or a sea with important tides. Assuming that at a speed of the water of 4 m/s, one turbine rotates at 60 RPM and produces 100 kW ...
• 669
25 views

### Would a 100-m tall wave really get reduced to near-zero height by hitting a West Cost style continental shelf, before reaching the actual shore?

This seems to be the conclusion of a 1996 study but the US Defense Nuclear Agency (which was renamed since then). Short shelf there refers to a West Coast style situation, known to allow for higher ...
• 306
36 views

### Are all turbulent flows chaotic?

I have often read that all turbulent flows are chaotic. I have come across a few explanations on web forums, but are there any authoritative references/textbooks that explicitly cover this question?
• 629
31 views

### Zel'dovich, Raizer - derive energy equation

Consider following excerpt from Zel'dovich, Raizer, Physics of Shock Waves and High Temperature Hydrodynamic Phenomena: I wonder how exactly can I derive (1.10) from (1.9)? For example, (1.9) ...
• 74
29 views

### What is average force?

When reading about how to calculate the force exerted from a liquid on the sides of a container it’s said that the average force is equal to 1/2hA x pg what is the meaning of an average force here? ...
1 vote
10 views

### How do I quantify an adhesive's ability to stick in contrast to flow?

Let's say you glue a ball to a shovel. How do you quantify this adhesive's and ball's ability to stick to the shovel, moving at different speeds, in air and then while the shovel digs into the ground? ...
• 193
28 views

### Force required to move a liquid through a specified opening

If I know the rate of a liquid, the density of that liquid, the velocity of the liquid, and the size of the opening. How would I calculate the force required (in PSI) to move that liquid through the ...
37 views

### Calculating hole size on the side of a pipe

I have a fluid channel through which a fluid with known properties (viscosity, density etc.) flows at a known velocity with a known pressure and temperature and mass flow rate. The external pressure (...
13 views

### When using pressure energy to state Bernoulli's Theorem, why do we say it's simply pressure?

I was asked this question in my viva and I couldn't answer. I know there's the whole mathematical explaination of this, when we multiply Force/Area with displacement and convert it into Energy/Volume, ...
1 vote
26 views

### Equilibrium of air volume in and out of an inflated bag

I want to use a small squirrel cage fan to blow air into (and inflate) a closed bag. The bag will also have a number of small holes in it to release air at various points across the bag. But, I want ...
• 11
1 vote
51 views

1 vote
39 views

### On taking the gradient of a compressible fluid potential

In literature I read: $$\tag{1} \mathbf{q}=(Nd^2)(\rho/\mu)[\mathbf{g}-(1/\rho) \nabla p]=\sigma \mathbf{E}$$ which is valid for liquid generally, and for gases at pressures higher than about 20 ...
• 1,235
26 views

### Can we really treat air and water flows the same?

Suppose we push water through a huge (0.1 m diameter) glass pipe and make an experimental Moody chart from slow (0.001 m/s laminar) to fast (10 m/s turbulent) speeds by measuring the pressure gradient....
• 996
9 views

### Can we use Darcys flow equation through porous media for pipe flow?

I am looking at flow in a pipe with no solid matrix. Therefore, the porosity is always equal to one. For such a set-up, I can use the Direct Numerical Simulations (DNS) on a 2D framework. However, a ...
• 1
1 vote
54 views

### Energy-momentum tensor of a perfect fluid flowing at the speed of light?

The general energy-momentum tensor for a fluid is given by (working with $c=1$ convention) $$$$\label{T}\tag{1}T^{\mu\nu}=\left(\rho+p\right)U^\mu U^\nu+p g^{\mu\nu}$$$$ with ...
• 1,429