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

learn more… | top users | synonyms (1)

0
votes
1answer
61 views

Why can't it work? Perpetual motion machine [duplicate]

Lets assume that the red ball is more dense than the white fluid and less dense than the blue fluid. The fluids are of very low viscosity and the machine can be of any height. The flaps open when ...
3
votes
0answers
39 views

To what depth can a whirlpool descend & would a barrel save you being pulled down?

My question is based around comparing the physics of a tornado against, what I imagine/assume to be the marine equivalent of a tornado, that is a whirlpool located either at sea, in a tidal region or ...
0
votes
0answers
29 views

How to make two equations dimensionless?

I recently got set this problem and am having trouble scaling the resulting equations. Any help would be appreciated. An incompressible thermal conducting fluid is contained between two infinite ...
0
votes
0answers
6 views

Measuring Steam Flow with Venturi Effect?

I understand steam is a compressible fluid and that the Bernoulli effect has been generalised for compressible fluids but I'm struggling understand how the Venturi effect can be generalised to allow ...
0
votes
0answers
19 views

How do i calculate the amount of fluid flowing through a tube?

If I have a tube with an internal diameter of 3.5mm in inside diameter and 30cm in length with a viscosity of 1.77cp, and a pressure of 200kpa, how fast will the liquid flow through? It the tube is in ...
-3
votes
0answers
16 views

Controlling the flow of powder from a container, based on grams selected [on hold]

was wondering how you would control the flow of powder from a container (with a small cylindrical dispenser at the bottom). The container is filled with powder. As the container drains, less ...
2
votes
0answers
38 views

Flow between two infinite plates [on hold]

I recently got set this problem and I was wondering if anyone would be able to give me some hints/intuition on how to solve it. Thanks. An incompressible thermal conducting fluid is contained between ...
0
votes
0answers
13 views

Work done by flow of a fluid

I'm looking at the power a flow of steam when used by a turbine. I originally assumed that the kinetic energy of a moving section of steam was equal to (let $V$ be volume, $\rho$ be density, and $v$ ...
0
votes
4answers
68 views

Why do not the ripples on a pond form a 3 dimensional wave?

I can see that that the expansion of the the circles happens in a two dimensional plane. Therefore, we say that a two dimensional wave is formed. But, why cannot we count the vertical disturbance so ...
28
votes
2answers
3k views

Pouring oil on choppy water to calm it , does it work and if so how?

Near where I live, local fishermen often bring cans of castor oil with them, to calm the water around their boats, if they feel bad weather is due. They claim this method of sea calming works, ...
0
votes
0answers
22 views

What are main differences between Lagrangian and Eulerian description? [on hold]

What are main differences between Lagrangian and Eulerian description? What are advantages and disadvantages of each of them?
-1
votes
0answers
24 views

water pressure for various pipe diameter if water tank pressure is known [on hold]

can anyone help me out please.. I have a water tank which is 20ft from the outlet and the capacity is 1000lt. pressure from this water tank is 8.66psi. Now how to calculate the water pressure for ...
1
vote
0answers
23 views

Aerodynamic noise created by cooling fan

What is the reason behind the noise created by fan blades while moving? Some paper says that it is because of the Kármán vortex street but it can be formed in static bodies only. Most of the ...
1
vote
2answers
51 views

The pressure in a container of water is based on depth. So what happens if I remove the bottom of the container?

So I understand that if we have a system that involves a container of water the pressure will equal atmospheric pressure at the top and as we go further down the container the pressure will increase ...
0
votes
1answer
37 views

Would opening a car door at high speed change the path of the car? [on hold]

If I were to open a standard, four door, four wheel, car on the highway, would the door swing open and possibly tear off? Would the drag that it creates 'reroute' the car (turn it to the direction of ...
2
votes
1answer
48 views

Under what conditions is air is in chemical equilibrium?

I am considering the flow field around a hypersonic glide vehicle at $M=7$. As I understand it, air is in chemical equilibrium if the fluid time scale $t_f \ll t_c$, where $t_c$ is the chemical time ...
1
vote
0answers
21 views

Anti-centrifugal force? [duplicate]

I put some balls (denser than water) in a bucket. I took a stirring rod, and swirled the water in one direction. The water became low in the middle, and high along the edges (centrifugal force). But ...
15
votes
1answer
2k views

Can I move an oil tanker?

Let's say that I'm standing at the edge of a basin made of concrete. This basin is filled with salt water and a ship floats on the water close to the edge of the basin. The ship is neither anchored ...
0
votes
0answers
40 views

What's the best language for physics modeling? [closed]

Hello every one can you tell me which language is better for CFD and also complex systems? C++, java or fortran? Can you tell the advantages of these languages to each other?
0
votes
2answers
57 views

Why is raindrop spherical in shape? [duplicate]

As the topic suggests why the raindrop is spherical in shape? Why it is not triangular or bipyramidal or tetrahedral? Is centre of mass or density of water related to it?
0
votes
1answer
17 views

What is the total velocity/force on a particle in fluid?

I am now facing a fluid-particle interaction problem. I would like to simulate particle motion in a fluid. I do know the external force acting on a particle (dielectrophoretic force in this case) ...
1
vote
0answers
46 views

Conservation of Mometum in integral form

Water is pumped from one reservoir into a another. The pipe expands after a lenght of $L/2$ to a diameter of $d$. Given: $\dot{V}_p, \rho_w, d, \eta, L, p_p$ The previos tasks allowed ...
2
votes
2answers
90 views

Why does a continuous water stream form ripples when colliding with a surface?

I was in the shower one day washing my hair, and noticed that the water falling off my hair formed perfect streams that ceased to break into droplets for quiet some distance (probably about 5-6 cm). ...
1
vote
0answers
16 views

Hard Drive Air Bearing Questions [closed]

I have a few questions related to the physics of the air bearing and head movement in a hard drive. What is the origin of the air bearing between the spinning platters and the head? Is it air ...
0
votes
0answers
40 views

What is the physical fundamentals of Pascal's law

Pascal's law or the principle of transmission of fluid-pressure (also Pascal's Principle) is a principle in fluid mechanics that states that pressure exerted anywhere in a confined incompressible ...
0
votes
0answers
32 views

Vacuum pressure equivalent in a siphon hose filled with water?

So, I was thinking about how siphons worked today, and no matter how high or low the tube goes, as long as the end is lower than the start, water will flow. So, if you took a hose, ran it up 50 ...
1
vote
1answer
20 views

Adding fluctuations to a hydrodynamic simulation to trigger instabilities

I'm doing a 2D combustion hydrodynamic simulation and there's a hydrodynamic instability that should be triggered because of the particular physical properties of my system. The key to the instability ...
1
vote
1answer
38 views

Good book for learning fluid statistics

I'm currently using Gray and Gubbins Theory of Molecular Fluids to learn about the statistical physics of fluids. It may be a fine reference text, but I'm not impressed with it as an introduction to ...
1
vote
0answers
30 views

On deriving a fluid flow pressure drop model using either physical theory or empirical methods

I'm trying to derive a model from physical principles of fluid flow, a simple quadratic model that tends to well fit actual pressure-flow data. For (real) subsonic air flow (ideally adiabatic) ...
0
votes
1answer
26 views

Thermodynamics about turbines

1.A turbine is rated at 650 hp when the flow of water through it is 0.85 m3/sec. Assuming an efficiency of 84%, what is the head acting on the turbine.
0
votes
1answer
57 views

Euler equation: momentum conservation in terms of enthalpy?

So I stumbled upon this equation: $\frac{\partial h v}{\partial t}= - \nabla(hv \cdot v)- \nabla P$ where $h$ is enthalpy, $v$ is fluid velocity, $t$ time, and $P$ pressure. It seems to have the ...
13
votes
5answers
632 views

What does it mean for a physical quantity if its mixed second partial derivatives are not equal?

This goes for every problem (either in electromagnetism or fluid dynamics) that has to do with vector fields. Say we have a fluid flowing in a closed circular pipe (or an electromagnetic field, the ...
0
votes
1answer
60 views

Shape of water jet

Suppose you are shooting a water jet in a vacuum vertically onto a flat plate in a gravity-less room. The jet makes a right angle to the plate and water is assumed to be incompressible. The mass ...
0
votes
1answer
43 views

Convective boundary condition

Consider a fluid over a sheet which is placed horizontally along the x-axis. The lower face of the sheet is in contact with another fluid at temperature $T_f$ ( it is heating the sheet). The sheet is ...
0
votes
3answers
58 views

How does the dissolution of salt affect the solution density?

Suppose you have a container of water as a solvent and you a certain amount of salt as a solute sitting at the bottom of the container that has yet to start dissolving. Supposing temperature and ...
0
votes
1answer
36 views

Is a convergent-divergent nozzle a perpetual motion machine of the second kind?

As answered in this question, a convergent-divergent nozzle (de Laval nozzle) accelerates a gas flow by converting its heat energy into kinetic energy. My intuition says that this violates the second ...
1
vote
1answer
43 views

Will a gas rotate as fast as the spherical container it is contained within?

Let's say I have a sealed spherical glass container 30 cm in diameter which contains plain air. The glass container is rotated about its axis at 1 revolution per minute. My question is, would the gas ...
0
votes
0answers
22 views

What is the meaning of the point of inflection in this?

Consider the following flow velocity profiles near a boundary, and the boundary profile point of inflection,PI Regarding the effect of pressure gradient on boundary-layer profiles does the point of ...
0
votes
2answers
43 views

Calculate Potential [closed]

$\vec{w} = \begin{pmatrix}w_r \\ w_{phi} \end{pmatrix} = \begin{pmatrix}\frac{Q_0}{2 \pi r} \\ 0 \end{pmatrix} $ 1) Show that the flow satisfys the continuity equation 2) Show that $\vec{w}$ ...
3
votes
1answer
26 views

How does a body accelerate that is put into a flow field with constant speed?

Imagine an infinitely long flow channel filled with water flowing at a constant speed everywhere parallel to the infinitely long dimension of this channel. Furthermore, imagine we place a body (say a ...
3
votes
2answers
80 views

Why is the Reynolds number “the way it is?” Why is its order the way it is?

Why is the Reynolds number “the way it is?” Why is its order the way it is? I'm not sure if this is an appropriate question for this context, but I would like more intuition on this matter and so ...
1
vote
0answers
36 views

Has there been any research done in fluid dynamics within a mobius strip?

I was wondering if there has been any research done with the flow of fluid within a mobius strip? The reason I am interested is, assuming the fluid would flow around a center axis point, at certain ...
1
vote
3answers
55 views

Laminar vs Turbulent flow separataion

(Left is a laminar separation, Right is a turbulent separation) I have been having a bit of trouble understanding this concept. How come the laminar separation involves a much larger wake than the ...
0
votes
2answers
24 views

Constant RPM of Gas Compressor

I would like to improve my understanding of gas compressors. If the compressor is moving at constant RPM, does it mean that it can only allow the same volumetric flow rate at all times? So the power ...
0
votes
1answer
36 views

Car window vibrating noise

I was going to ask a question similar to: Why, when one opens 1 car window, does that noise occur? but saw that it was already asked and answered very helpfully. However, there are a couple other ...
0
votes
1answer
73 views

Can a nozzle increase the thrust of a water rocket?

First of all, what is the correct equation to determine the thrust produced by a water rocket? $$ F_T = \dot{m} V_e \tag{1} $$ $$ F_T = \dot{m} V_e + (p_e - p_0)A_e \tag{2} $$ Using the first ...
1
vote
1answer
50 views

What is this form of mass conservation equation?

I found the following equation of conservation of mass (continuity) in "Computational Fluid Dynamics Vol.III" by Hoffmann: $$ \frac{\partial \rho}{\partial t} + \frac{\partial}{\partial x}(\rho u)+ ...
0
votes
0answers
44 views

Any applications of kinetic physics on cosmological scales?

On galaxy cluster scales, one is usually forced to use approximate theories such as hydrodynamics or magnetohydrodynamics for modelling cosmological phenomena. I wanted to ask if kinetic theory is ...
1
vote
0answers
23 views

Difference between a tap and a hosepipe

When the flow of water through a tap is blocked by the fingers, the water does not increase in velocity whereas the velocity of water increases when the same is done tp a hosepipe. Both involve the ...
1
vote
1answer
26 views

Reynolds Average Navier Stokes equations and turbulence scale

To obtain the time average of an unsteady term like $\frac{\partial u_{i}}{\partial t}$ by definition we perform the following: \begin{align} \overline{\frac{\partial u_{i}}{\partial t}} &= ...