# Questions tagged [fluid-mechanics]

Questions relating to fluids at rest (fluid statics) or the forces and effects of fluids in motion (fluid dynamics).

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### Navier-Stokes Problem

I've been trying to solve this problem for a while now. I've tried simplifying and finding boundry conditions (such as the no-slip condition), but I can't seem to simplify it enough to make it ...
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### Flow across V-notch

I have an exercise where I have to calculate the flow that passes through a V-notch with the angle <$\theta = 150 ^\circ$> and the head h1. The notch has an upward going slope. (I don't know if ...
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### Submerged fraction buoancy force

How can I calculate the height of the submerged part of a partly filled bucket? (The liquid both inside and outside is freshwater). The bucket is trapezoidal such that the volume of the submerged can ...
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### Centrifugal pump head-flow prediction with CFD

Given a volute pump casing, the impeller, and RPM how would one obtain a simulated head-flow graph? As for what I have seen in research papers most methods already assume input flowrate / pressure and ...
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### Vertical pipe flow

I want to know the flow through a vertical pipe when a valve in the bottom is opened (a disk is lowered as illustrated in the drawing) I know the heights in the drawing and the diameter of the pipe. ...
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### Do curves and bends in an airduct (or airpipe) influence the energy that can be captured from that airflow?

To better explain my question, I've included a schematic below. Let's assume that the water level rises. As the water rises in the wide chamber, it displaces the volume of air and essentially pushes ...
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### How to calculate the Knudsen number?

when calculating the Knudsen number: $$Kn=\frac{\lambda_{mf}}{L}$$ Where $\lambda_{mf}$ is the mean free path of a molecule, and $L$ is the characteristic length. How is the characteristic length ...
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### Does stress have to be isotropic in fluid under static equilibrium?

Does the Cauchy stress tensor under static equilibrium in a fluid HAVE to be isotropic? If so why? I would like to be pointed to rigorous mathematical resources that show this. What physical ...
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### How could Adrian Bejan's 'Constructal Law' be formulated mathematically?

Adrian Bejan is known for having devised a very interesting theory for the hierarchical and aesthetic structure found in nature, from the branching tree shape of river deltas to the tree shape of ...
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### Hydrostatic force acting on a hemispherical impression

Consider vertical wall which contains a hemispherical impression as shown. Water is filled only upto the centre of hemispherical impression, i.e. to a depth of L. It is required to know the horizontal ...
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### Dimensional Analysis for Fluid Dynamics: Shear Stress Exerted By A Fluid

I'm confused by how the dimensions for a Fluid Dynamics problem make any sense. (Yes this was homework, that I've already completed and submitted, I'm just trying to learn the concept). Anyways, you ...
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### Why air cannot be used as a cooling medium in CO2 refrigeration system?

Can anyone please explain the reason for above question?
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### Solve an Air Conditioning condensate drain problem

While working from home (a 1968 build retrofitted with A/C) here in FL I've noticed that my A/C drain makes a gurgling sound. I've traced the sound to the condensate drain pipe which appears to be in -...
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### Can ocean flows after a crashing wave be accumulated in one point to increase the water height of that location?

Here in this image, you can see the water flow onto the beach to a certain distance. After a while, the water retracts back. If I put a V-shaped collector (like a vertical standing open book) facing ...
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### How do i calculate, and make sure that the same amount of water comes out from every hole in my pipe?

I need to distribute the water evenly between five holes in my stainless steel pipe. How do i calculate which size the different holes need to be, in order to get the same amount of water out of each ...
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### Will any buoyant force act on the block when it settles at the bottom?

Consider a cylindrical container that is filled with water to the rim. Now, an iron block of Volume $V$ is dropped slowly into the container. The volume of the water that spills out will also be $V$, ...
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### Does pressure/temperature drop in a funnel or nozzle with a gas being pumped through it by a fan

So, I was thinking about trying to build some kind of body cooling suit and started looking into the wonderful world of refrigeration systems. I've managed to get myself side-tracked pretty badly ...
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### Heat added per unit mass in a cylindrical pipe

I have a question, which seems simple, but for the life of me I cannot figure out. So, let's say I have a very thin cylinder (consider an interface), between two fluid with different temperatures. The ...
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### Can the crest of an ocean wave be increased by directing ocean waves to a center of a curved column?

My question really pertains to improving the oscillating water column device to generate greater electricity. The way the current system works, when a wave with a crest hits the wall, the water inside ...
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### Why $\frac{m}{V}$ gives average density when density varies?

This might be a very basic question, and for years I have gone by simply accepting it as a fact. That whenever the density is uniform the formula $\frac{m}{V}$ gives that uniform value of density and ...
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### How does decreasing the cross-sectional width of a channel impact steady flow?

The continuity equation states that for a constant mass flow rate, if the cross sectional area of a channel is decreased, then velocity is increased. What happens if the channel has high walls and is ...
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### Effect of air flow speed on thermal time constant

Suppose a simple case : A fan blows air on a rectangular object made of aluminium. If you need to add some dimensions to the object, do not hesitate The air speed is at X m/s and the air is flowing ...
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