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

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30 views

Meaning of imaginary eigenvalues in advection equation

I'm reading the book Fluid Simulation for Computer Graphics (Amazon link), and stumped by the following sentence in Chapter 3: what's happening is that the eigenvalues of the Jacobian generated ...
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1answer
198 views

Position based dynamics constraint scaling factor

Reading through Müller et al., Position Based Dynamics, 2007 I got lost when passing from equation (5) $$\Delta p = \frac{C(p)}{|\nabla_pC(p)|^2}\nabla_pC(p)$$ to equation (6) (and applying the ...
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1answer
147 views

Flow rate through hole at bottom of tank, estimate time for depth to reach 1 foot

I am a structural engineering student and have limited experience in fluid dynamics. I'm not quite sure if I'm going about the problem in the correct way. The question is: An open cylinder of ...
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2answers
194 views

Do wind turbines convert the kinetic energy of air?

It is often said that wind turbines convert the kinetic energy of the wind into electricity. But in respect to horizontal wind turbines with airfoil shaped blades this is imho not the case. Wind ...
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0answers
35 views

Solve unsteady state Bernoulli equation for flow in a pipe

I am an engineer studying an unsteady-state flow through a pipe. The Pipeline has been cleanly cut into two halves, without deforming the cylindrical form of the pipe, exposing the contents to ...
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1answer
163 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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0answers
47 views

Viscous drag proportional to $r$ or $r^3$?

When a spherical object is falling at terminal velocity through a fluid: $W=U+F$, where $W$ is weight, $U$ is upthrust and $F$ is viscous drag. Rewriting, using Stoke's Law, we get: $$\frac{4}{3}\pi ...
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6answers
538 views

Physics of how the cochlea isolates frequencies along its length?

Can anyone explain the separation of frequencies along the basilar membrane of the cochlea please? (equations would be nice) I understand it being related to the resistance caused by fluid in the ...
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1answer
103 views

Estimate the time spent along fluid flow

I have a 2d flow field with a singular point $$\dot x=y-px^2\\\dot y=-x-qy^3$$ where $p,q$ are small parameters. How do I compute the cost time of a particle from $(x_0,y_0)$ to ambient of the ...
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18 views

Ocean surface mean current flow meaning

I tried to simulate the trajectory of an drifting object in the oceans by using the data of the OSCAR project http://www.oscar.noaa.gov/. The dataset actually used consist of grid sampled mean 2d ...
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1answer
45 views

What are premultiplied energy spectra?

When speaking about turbulence in fluid mechanics many times authors speak about "premultiplied energy spectra" but they never explain what really it is. I have searched for a definition but I did not ...
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1answer
3k views

What is the difference between dispersion and diffusion?

What is the difference between dispersion and diffusion? Currently I believe, that diffusion is the mixture of molecules due to Brownian motion. So I read everywhere, that it happens with magnitude of ...
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1answer
111 views

How does a sonic black hole (or dumb hole) work?

I came across this term and I heard they used sonic black holes to detect something analogous to hawking radiation, but I have failed to find sources which explain how exactly they work and how they ...
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1answer
44 views

Finding volume of water that emerges from opening per unit time [closed]

A rectangular opening (width w and height h2-h1) is cut into the side of an open tank. The water doesn't emerge in a uniform velocity. Assume that SA of tank >> area of opening. I'm trying to study ...
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1answer
370 views

Why are mass flow rates found using Venturi meter and pitot tube different?

Regarding an experiment to find the mass flow rate of a fluid (air) using a venturi meter and a pitot tube: What could be the cause of a variance in results obtained using the 2 instruments mentioned? ...
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0answers
50 views

How to model the dissipation term

When a solid particle which is moving with $V_p$ collides with a droplet which is falling with $V_d$, based on what reported in literature, a liquid skirt will be formed as shown in figure below. One ...
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1answer
79 views

Nomenclature clarification concerning solitons

My experience with solitons is restricted to the classical setting, namely solutions to the quartic interaction $\phi^4$, the Sine-Gordon equation, and Korteweg–de Vries equations. I was explicit to ...
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2answers
118 views

How to calculate liquid pressure regardless of the gravity?

Assume we have a balloon in a tank filled with a liquid , without any gravitational forces: We just know the Temperature, V0 and V1 I want to calculate the pressure exerted from the liquid on the ...
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1answer
601 views

Finding Surface Tension of water at certain Temperature and Pressure

The question is: Using the Young-Laplace Equation (if applicable), find the surface tension (dynes/cm) for water at 20 degrees Celsius with 2.5 psi. Round to the nearest tenth. ...
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2answers
54 views

Numerical modelling of a step function in time in a hydrodynamic system. (Runge Kutta fourth order)

So I'm trying to model a hydrodynamic system that introduces a sudden "jump" in the value of a function at a specific time. The system is solved with a Runge-Kutta fourth order method. I have a ...
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1answer
19 views

Does the length of a pipe influences the flow?

if I have a closed system of horizontal pipes, filled with water, where I want to create a flow at some rate by using a pump. Does the length of the system influences the flow ? (in real world not in ...
2
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1answer
106 views

How to move liquid uphill against a thermal gradient, without moving parts

I am looking for a conceptual way of dealing with the following. I am not looking for a set of blueprints. Consider a 5 meter x 10 cm vertical closed tube filled with a substance in the gas and ...
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2answers
47 views

Why is the solution to the Blasius boundary layer problem self-similar?

In every course or textbook that I encountered so far, the authors transform the Navier-Stokes equations of the Blasius boundary layer problem into the Blasius ODE. The problem with many of those ...
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1answer
502 views

Torque on a rotational cylinder in viscous fluid

I've been stuck on what I'm pretty sure is a simple part of a larger question. It's a cylinder (radius a) spinning in a viscous fluid. It's rotating at rate $\Omega$ .During this question we get that ...
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24 views

Is a 3D or 2D Poisson's equation separable or non sperable? [migrated]

Can someone please explain to me if a 2/3D Poisson's equation is separable or non separable? Thank you
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1answer
31 views

can ice crystals be molded into a structural shape in space

I know that water exposed to vacuum space first boils and then turn into vapor (sublimates) . Is it possible re use this vapor say inside a pressurized membrane, to mold it into a solid ice structure, ...
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1answer
30 views

Static pressure in ducts and its dependency on speed flow and density

I know that depending on the duct circuit (bends, complex geometries...etc), the static pressure will be defined. If we assume air is flowing in the circuit with varying speed and/or varying density. ...
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1answer
29 views

Cosmology: collisionless vs collisional fluids?

I try to understand the difference between collisionless and collisional fluids in cosmology. My first question is the following. In the context of FLRW cosmology, we suppose that the Universe can ...
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1answer
140 views

Orifice Jet Flow experiment

I am writing up a report on Orifice jet flow experiment in which I am required to find coefficient of flow velocity, $C_v$, and the Coefficient of discharge, $C_d$. There are couple of things that I ...
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2answers
274 views

How come a whistling kettle starts whistling only when water boils, and not long before - due to hot air escaping under pressure?

A whistling kettle will start to whistle when the water boils and turns into a jet of steam which then exits the small aperture in the spout. But why doesn't this happen much earlier - when the air ...
5
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1answer
215 views

Why do some impact craters have an elevation in the center?

Why do some impact craters have an elevation in the center? What processes lead to its formation?
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1answer
208 views

Sum of forces with liquid in rotation

It's not homework (I'm teacher). I would like to compute sum of forces on this study : The shape is symmetrical like that I'm sure the center of gravity is in the center of the shape. I compute ...
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1answer
121 views

Positions and corresponding terminology of “acoustics energy”?

From limited knowledge, decades ago, dating back to the nineteenth century: Ohm's law of specific acoustic energies was the first biological application of Fourier's theorem. Actually, it was ...
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58 views

Locomotion at low Reynolds number with Gauge Theory

I've been studying some approaches with gauge theory to some problems in Mechanics and I've found the problem of self propulsion at low Reynolds number a quite complicated one. The approach I'm asking ...
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28 views

water is dropping from car? [migrated]

I bought a car yesterday Nissan 2009 , today i have noticed that water is dropping under the front passenger seat.is there any one knows what is the problem please.
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0answers
26 views

Deceleration of spherical particle in fluid

If I know the initial velocity of a particle entering a fluid, how can I calculate its deceleration over time ? What parameters would I need to know ? Viscosity of the fluid, weight of the particle ...
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1answer
54 views

Is there a speed limit for objects falling in gases or liquids? [duplicate]

Let $o$ be a spherical object with mass $m$ and surface $s$. Let $g$ be the gravitational acceleration and $h$ the height. Let the gas where we drop $o$ in have density $d$ and pressure $p$ at ...
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1answer
52 views

Exact solution to a 2D/3D Poiseuille flow in a channel

Hi everyone and thank you in advance for any help. I am struggling to find an analytical solution to either a 2D or 3D Poiseuille flow in a rectangular duct. All I can find is 1D example. Can someone ...
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2answers
73 views

Does the definition of compressibility depend on the frame of reference?

According to many authors, a fluid is defined to be incompressible if the material derivative of the density $\frac{D\rho}{Dt}$ is zero, that is to say, that in an frame of reference following the ...
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3answers
176 views

How does vasoconstriction/vasodilation of arterioles change blood pressure?

Background: I am coming at this question from an electrical engineering background, and I feel like I am missing certain assumptions that are going into the statement found in my physiology textbook, ...
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2answers
47 views

Will going up with a larger diameter ensure a higher water pressure in the distribution pipes? [closed]

Have a look at the drawing below describing a sample situation: a water tank a 1'' diameter pipe bringing the water down, inside the ground, arriving near the house in the house, 2 x 0.5'' diameter ...
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1answer
28 views

what force pump is needed to power [closed]

Im studying design have not got a good grasp on maths, but understand the working principles of pressure and water! my problem hopefully has included all necessary info in the image. Please help. ...
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3answers
122 views

Why does it seem as if big vehicles “attract” mine when I drive close to them?

When I drive a car at high speed and when I am near to another big car (like a van, or transport vehicle) I feel an attraction to or something push me toward the other big car . What's the physics in ...
3
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1answer
122 views

Nonlinear waves and shock formation

In the cases of nonlinear acoustics, why is shock formation unlikely when the dispersion is strong when compared to the nonlinearity of the wave?
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2answers
190 views

Speed of Sound/Push in Supersonic Flight

I've learned from things like the Veritasium Slink Drop and the old "break the speed of light by pushing on the end of a very long pole" thought experiment that objects have a "speed of push" which is ...
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2answers
182 views

Self Stirring Boiling Liquid

A couple of weeks ago, a friend and I were brewing a new batch of beer. We boil our wort in a turkey fryer. Pretty standard setup for beginners. Anyway, our wort was getting pretty close to boiling ...
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5answers
7k views

What's the surface area of a liquid? How does evaporation increase if the surface area of a liquid is increased?

Wikipedia says that a substance that has a larger surface area will evaporate faster, as there are more surface molecules that are able to escape. I think the rate of evaporation should decrease as ...
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0answers
13 views

Saturn's Hexagon [duplicate]

I am currently trying to understand the formation or indeed the explanation as to why the hexagonal north polar vortex on Saturn is exactly that: Hexagonal. I understand that the most prominent ...
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1answer
704 views

Pressure loss in a syringe

I'm currently working on a problem which is really giving me some issues. The problem concerns the force required to expel water from a syringe. We have a 20 ml syringe (which is $2\times10^{-5}$ ...