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

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Vortex shedding

So I was reading about vortex shedding, and got to know that it causes the building to resonate. Is there any way to use this resonance to generate electricity (maybe use quartz?) I am trying to make ...
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61 views

Collision of multiple fluid flows at a point [closed]

I would like to do an analysis when two or more fluid streams flowing from different direction with different velocity, meet at a point. What happen after the collision? Are there any related studies ...
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120 views

Why does the blade height goes on decreasing in a multi-stage axial flow compressor? [closed]

The axial compressors used in jet engines have their blade heights in decreasing order in the direction of the flow.
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1answer
81 views

Power of viscous friction on a falling sphere

I have derived a simple model of a rotameter using an homogeneous solid ball in a rigid cone where a fluid flows. I consider 4 forces: Weight, Buyancy, Viscous Friction and Drag. I have written my ...
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0answers
92 views

What is the magnitude of the sound that a Helmholtz Resonator attenuates?

I know that the shape of the Helmholtz Resonator, specifically its neck shape and the volume of its cavity, determine the resonance frequency of the resonator. Moreover, the resonance frequency is ...
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1answer
2k views

$\Delta T$, temperature units. How to use fahrenheit in this formula

To calculate the power in a fluid with a flow, the following formula is applied: $$P = \Delta T \rho c_p \times flow$$ $\Delta T$ can be entered as both Kelvin and Celsius. But what if I want to use ...
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1answer
151 views

What does the absence of hydrodynamic entrance effects do to the momentum conservation Equation?

I am trying to do a homework problem where we re-write the mass, momentum and energy conservation formulas for downward flow in a vertical pipe and it says "where all hydrodynamic entrance effects ...
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0answers
78 views

Rotated glass with water

I think most of us know the experiment where you fill a glass with water, cover it and then turn upside down(holding the cover). You can read about it here I thought that it would be fun to do some ...
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2answers
312 views

Breaking ocean waves on other planets possible?

I have always wondered if there were an ocean on another planet with stronger or weaker gravity, would it be possible to have breaking waves?
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293 views

does the rate of change of height varies for different fluids?

I decided to experiment for the rate of flow of liquids (like water, oil, acid, etc) from a burette. I decided to use Torricelli's law $v=\sqrt{2gh}$. When experimenting, the time taken for a viscous ...
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6answers
52k views

Relation between pressure, velocity and area

In a nozzle, the exit velocity increases as per continuity equation $Av=const$ as given by Bernoulli equation (incompressible fluid). Pressure is inversely proportional to velocity, so we have lower ...
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1answer
137 views

gas pressure outside nozzle in vacuum

I'm currently trying to figure out the following in the simplest possible way: Say we have a nozzle in a vacuum environment. A gas of a certain pressure is emitted through the nozzle, which has a ...
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0answers
83 views

How does this help an aeroplane to fly? [duplicate]

I read it somewhere on the internet that wings of an aeroplane are designed in such a way, that they increase the velocity of air above the wings and so pressure above the plane becomes less than the ...
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1answer
220 views

Sailing against the wind. Is this a fair model?

I was ruminating the explanations about how boats can sail against the wind (or "into the wind"), and wondered if one could devise a simple mechanical model without hydrodynamics involved. Imagine a ...
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1answer
112 views

Non-determinitric flow of water stream on vertical porcelain surface

I noticed several times while washing my hands that accumulated water when starts streaming vertically does not flow vertically in straight line on vertical porcelain surface under the force of ...
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2answers
747 views

Efflux speed of ideal fluid dependent on diameter?

I have a cylinder full of water with diameter $D$ with a round opening on the bottom with diameter $d$. The water is friction-free and incompressible. Now I need a relationship for the efflux speed ...
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1answer
128 views

Blimp challenge. Doubts about volume at different heights [closed]

I want to design and build a small semi-rigid airship/dirigible. It will be controlled with RC so I will install motors, arduino, battery etc. Filled with helium. Weight of the equipment is about 2kg ...
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3answers
197 views

Explain Turbulence [closed]

I'm a high school student. I still don't understand what turbulence is. Please can you explain what it really is? This is what I think it is: rotating motion of water when a particle travels at a ...
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2answers
384 views

About how fast can a small fish swim before experiencing turbulent flow around its body? [closed]

About how fast can a small fish swim before experiencing turbulent flow around its body? An Engineering Problem! Please go through this question step by step. :D
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1answer
166 views

How to calculate fluid(oil / hydrocarbon) loss under pressure

I'm trying to calculate the amount of fluid that would flow through an area dependant on the amount of pressure that there is. I'd also like to know the rate at which it would flow. Essentially I ...
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1answer
287 views

Will Buoyant Force Change If The Container is Accelerated Up or Down?

If we have a fluid which is in a container that is accelerated, say, upward by $a$. Then, what will be the buoyant force on an object with volume $V$, Density of liquid, $\rho$? I believe it will be ...
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2answers
328 views

How does the pressurization in a house's water supply allow adjustable flowrates from a tap?

John Rennie's answer to this question got me thinking about the water supply in a house. I know that water supplies are normally operated at an over-pressure with respect to atmospheric pressure to ...
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2answers
552 views

Differences in the behaviour of pinching a garden hose and closing a tap

Let's say you have a garden hose connected to an ordinary water tap which is opened fully. If you pinch the end of the hose, water leaves the hose at a higher speed (and this can be useful while ...
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1answer
172 views

Smoothed Particle Hydrodynamics, Chemical Reactions and Stiffness [closed]

Dear people from stackexchange physics. I have been using SPH for quite a while to simulate free boundary flow, and just recently we tried to include some kind of (simple) chemical reaction in our ...
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1answer
1k views

Deriving shallow water equations from Euler's equations

I would like to derive the one-dimensional shallow water equations from Eulers's equations. This works perfectly for the conservation of mass. Especially the meaning of the longitudinal fluid ...
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1answer
95 views

Conservation of mass in fluid flow

When deriving the continuity equation in physics class for two immiscible fluids flowing in succession we used the principle of conservation of mass. My question is, shouldn't volume be conserved ...
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1answer
110 views

What is the physics concept in sponge filter

I really need help I want to ask what is the physics concept in Sponge Filter?
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1answer
152 views

Energy conservation at a the end of a hose pipe?

I am trying to figure out the energy balance at the end of a hose pipe with water pouring out. Applying Bernoulli's equation inside the pipe we have three energy terms: Kinetic energy, "pressure" ...
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1answer
381 views

Pipe in a flowing river problem

I'm working on a certain problem in fluid mechanics, which isn't really my strongest area. The problem is as follows: Curved pipe is partially submerged in a flowing river so that one end is pointing ...
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0answers
61 views

Approximating density from pressure and flow

I want to get the density of a fluid going through a pipe. I can measure the flow and pressure with a flowmeter and the temperature using a thermometer. With this information, I want to calculate ...
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3answers
191 views

Spontaneous motion in a wind tunnel

Suppose that a hollow truncated cone is placed in a wind tunnel with a steady wind speed $V$. The cone is placed in such a way that it's base of area $A_1$ faces the wind (rather than the other side ...
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1answer
174 views

Does the space between molecules have no pressure?

In any living organism there exists are space between cells filled with interstitial fluid. Loss of this fluid into abnormal areas (3rd spacing) can cause relative to severe hypo-volemia. The fluid ...
5
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1answer
681 views

Why does a container with fluid make different sounds at different fluid levels?

Have you ever noticed that when you are filling a container with fluid. As it approaches the top, it makes a different sound? You can tell by listening when your about to reach the top. Why is this?
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1answer
955 views

How fast does the water travel down river when the discharge gates of a large dam are opened?

How fast does the water travel down river when the discharge gates of a large dam are opened? Can the discharge-wave travel downstream faster than the water? Is this likely to occur for a real river ...
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2answers
96 views

Air pressure in closed (circular) tube

I have learned that for fluids and gases $P_\text{total}=P_\text{dynamic} + P_\text{static}$. Suppose we have a closed circular tube in a form of ring filled with air under some pressure. In this ...
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4answers
405 views

Pressure in fluid mechanics of incompressible liquid

Most liquids can be approximated to be incompressible, since the Mach-number is much smaller than 1. That means that the density variations are negligible and from the relation between pressure p and ...
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1answer
302 views

When to use ideal gas law in fluid mechanics?

The ideal gas law (aka the equation of state) is given by $$ p/\rho_N = k_BT, $$ where $\rho_N$ is number density. When am I allowed to use this to describe a fluid?
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3answers
2k views

How to freeze the Niagara waterfalls?

Here is a picture of the usual vigorous Niagara Falls (in the winter). Here is the picture of Niagara Falls frozen in 1933 (in the very cold winter). Here is the picture of Niagara Falls frozen in ...
5
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1answer
136 views

Transport theorem derivation question

I am trying to rigorously go through some fluid mechanics proofs and theorems. I am currently going through a proof related to the transport theorem and I am having trouble with a step. The steps in ...
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4answers
3k views

Festive physics: gold flake vodka

I have a bottle of vodka that has a load of gold flakes suspended in it. It has been sat still for over 24 hours and the flakes are all still suspended within the liquid: they have not risen to the ...
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1answer
178 views

Is it possible to use the parabolic shape of a rotating fluid to measure the angular frequency of the rotation of the Earth?

A fluid in a rotating bucket will take on a parabolic shape (for example of some simple derivations of this result see http://en.wikipedia.org/wiki/Bucket_argument). The assumptions that play into the ...
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1answer
204 views

Acceleration of particles in a pipe with variable cross section

I am currently making an exercise from Paterson,1983, IV.3.ii. It goes as follows Water flows steadily and incompressibly along a pipe whose area cross section $A(x)$ varies slowly with the ...
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1answer
237 views

Maximum liquid velocity in a siphon

According to wikipedia: Siphon, the velocity of liquid in a siphon is equal to $\sqrt{2gh}$, where h is the difference in level between the water surface and the opening of the siphon. But it also ...
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2answers
388 views

What is the aperture in the hydraulic analogy of Ohm's law

Note: My question is duplicate of Why doesn't water come out of tap/faucet at high pressure when I turn it on?. None of the answers given there explains how the continuity equation fits properly. ...
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1answer
105 views

shear and normal stresses

When we talk about shear stresses in a fluid, we find that the shear stress is given by $$\tau_{xy} = \mu(\partial_y u + \partial_x v) = \tau_{yx}$$ This relation we get when only looking at one side ...
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2answers
15k views

Does pressure drop across pipe affect flow rate?

Let's say there is a main pipe containing $100\: \mathrm{m^3/hr}$ a fluid of density $750\: \mathrm{kg/m^3}$ and it's gonna be branched into 2 pipes (Pipe A and Pipe B) of the same diameter. If Pipe A ...
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1answer
221 views

Units of the PDF in the Lattice Boltzmann Method

In the Lattice Boltzmann method we require (based on mass conservation) that the sum of the distribution functions for a node is equal to the density, i.e. $$ \sum_i f_i = \rho $$ But what units do ...
2
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2answers
2k views

Physical description of momentum flux tensor

In the field of fluid mechanics, what is the momentum flux tensor? Is there an easy explanation for how it "works"?
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2answers
261 views

Freezing water in a closed container [duplicate]

We know that density of ice reduces by about 8% during freezing, this means it expands to have little higher volume. But if I fill water in a container (entire volume) which has very low coefficient ...
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1answer
129 views

Pressure difference between 2 side of wings of aircraft

I understand why the pressure is reduced above the wings of aircraft, but when I read books and look for information, it says that the air is compressed below the wings, I do not understand why it is? ...