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

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Fluid Mechanics with calculus on manifolds

Fluid Mechanics is a branch of physics that uses a lot of vector calculus in $\mathbb{R}^3$ to describe phenomena mathematically. Calculus on manifolds, however, is the straightforward generalization ...
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81 views

Branching lemon drop “smoke rings”

This might be hard to ask, but here goes nothing. I recently poured a cup of water into a black coffee cup. There was a light source--not very bright--above the cup. Anyways, I was squeezing a ...
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44 views

Could the phenomenon of vortex bursting be exploited to reduce wake turbulence?

One of the classic stories in the annals of aerospace engineering is the development (and subsequent redesign) of the F-18 and its Leading Edge Extensions (LEX) due to fatigue problems, problems that ...
6
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53 views

What is a superfluid in field theoretic terms?

I'm wondering how one precisely defines a superfluid in terms of the effective field theory description. In Nicolis's paper http://arxiv.org/abs/1108.2513 there seems to be an extremely simple ...
6
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68 views

Time inversion for Euler equation

Consider Euler equation for continuum body: $$\frac{\partial u^i}{\partial t}+\mathbf u\cdot \nabla u^i=- \frac{1}{\rho} \frac{\partial p}{\partial x^i} $$ where $\rho$ is the mass density, $p$ is ...
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212 views

Is a venturi pump feasible at very low pressure?

I need assistance (or experience feedback) in estimating if a Venturi pump would work at low pressure. A boiler under vacuum (10% atmosphere) will produce steam (at a given speed depending on the ...
6
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319 views

What's the efficency of a steam jet pump?

Jet pumps or venturi pumps are often stated as having a "terribly low" efficiency, steam jet pumps specifically are usually describes as "only justifiable when there's an abundant steam supply anyway" ...
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379 views

Can a divider “laminarize” turbulent flow and thus reduce friction?

Looking at the Moody chart I think to myself, the friction factor doesn't decrease much at all with Reynolds number after a certain point. I wonder if laminar flow is more efficient in a sense, and ...
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85 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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80 views

Do vortex tubes work with a reversed end plug?

Would a vortex tube still work if instead of a cone plugged into the 'hot' end you had a smaller hole on the 'cold' end? As I understand it, the point of the cone on the hot end is to only allow the ...
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1k views

Difference between Eulerian and Lagrangian formulation of Fluid Dynamics

Difference between Eulerian and Lagrangian formulation of Fluid Dynamics. I am completely new to fluid mechanics. Until now definition $F = ma$ was sufficient for me to solve any rigid body problems ...
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95 views
+100

Analytical solution of transient barometric formula for fluid in one dimension

Consider a column of fluid of length $L$, with initial density $\rho_0$ and initial velocity ($u_0 =0$) everywhere. Now at time $t=0$ gravity is switched on. No-slip boundary conditions are assumed at ...
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48 views

What's the corresponding symmetry of enstrophy conservation?

In fluid mechanics, especially 2D turbulence study, people talk about conservation of enstrophy. But I can't really understand enstrophy very well, and what's the corresponding symmetry of enstrophy ...
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61 views

Kolmogorov/Energy spectrum for turbulent boundary layer

Previously, I have calculated energy spectrum for 3D isotropic turbulent flow data which is equally spaced in all three directions and then to compute the energy spectrum, one performs Fourier ...
3
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151 views

Bubble in a pipeline

I am just thinking about this phenomenon: We have a horizontal pipeline with a flowing liquid, which contains a small bubble of gas. How do the dimensions of this bubble change when it reaches a ...
3
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0answers
89 views

Boundary layer equation

I was trying to understand the derivation of the boundary layer equations at p.145 of http://www.unimasr.net/ums/upload/files/2012/Sep/UniMasr.com_919e27ecea47b46d74dd7e268097b653.pdf. : the ...
3
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125 views

seemingly impossible query

While on an expedition to a lake, it was noticed that the wind speeds gusted violently in seemingly periodic wakes and the proposed explanation was Von Karman vortex shedding off of nearby mountains ...
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58 views

Where else in physics does one encounter Reynolds averaging?

Reynolds-averaged Navier–Stokes equations (RANS) is one of the approaches to turbulence description. Physical quantities, like for example velocity $u_i$, are represented as a sum of a mean and a ...
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56 views

Modeling the formation of a stellar system and matter accretion

I am trying to figure out what do I need to know to properly simulate the creation of a solar system from a particle cloud with random distribution of hydrogen atoms. Being more of a programming ...
3
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146 views

Conformal symmetry of Navier-Stokes?

This question is in reference to the paper arXiv:0810.1545 Can someone help understand this scaling argument and the proof(?) that there is a conformal symmetry in Navier-Stoke's equation? (..am I ...
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119 views

Difference between a Fixed Point and a Limit Point in implementations of the Renormalization Group (RNG) in Large Eddy Simulation (LES) model

In the introduction of this paper, it is explained that and how the application of a dynamic subrid scale model for turbulence into a large eddy simulation (LES) model corresponds to doing one ...
3
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0answers
72 views

Sound level of organ pipe driven by helium

The sound pressure level of an organ pipe is a function of the gas flow rate delivered to the pipe. Source Would the sound level of an organ pipe driven by helium be lower than that of a pipe driven ...
3
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0answers
222 views

Flow behind a plate causes pressure drop?

I've done an experiment where we direct an air jet from a fan onto a set of electronic scales. By measuring the velocity of the air jet at the exit of the fan nozzle, and applying the conservation of ...
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49 views

Euler equation with single state variables

I want to simulate a flow using the Euler equations. For this reason I'm wondering if there's a modified version of the Euler equations. At the moment my formula looks like this: $$ ...
2
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0answers
41 views

Fluid Dynamics Tsunami

I have been given a energy head (pressure) in meters for a given tsunami on land. My question is if the tsunami hits a wall 1 meter by 1 meter, is it possible to calculate the height it will reach. ...
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93 views

Taylor expansion in Lattice Boltzmann Method derivation

Currently I'm trying to understand Lattice Boltzmann Method for solving CFD problems. In its derivation BGK approximation is used to get rid of complicated collision integral. But when they come to ...
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39 views

Has this boundary condition been used in fluid flow?

I would like to know whether anyone has seen a boundary condition used in a fluid flow problem, of the following type. Suppose viscous incompressible fluid is to the left of a plane $x_1=a$, so the ...
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38 views

Translation symmetry and the non-conserved momentum in Viscous fluids

Even though a viscous fluid has a translation symmetry (invariance) for its Lagrangian , it still 'waste' Linear momentum. How come ?, isn't the rule that every symmetry yields a conservation law ?
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49 views

Is there any connection between “Lagrangian and Eulerian formalism of fluid” and “Heisenberg and Shrodinger picture”

Is there any connection between "Lagrangian and Eulerian formalism of fluid" and "Heisenberg and Shrodinger picture of Quantum mechanics"? Thanks!
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18 views

Regarding formulation of a multipoint model of fluid dynamics

Suppose I am trying to formulate a multipoint model of fluid dynamics. I have a procedure for doing so the details of which is not important to this question, but only that it is based on a series ...
2
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0answers
155 views

How does an atomizer work?

Will someone please explain how a basic pump atomizer works? I have a feeling it has something to do with pressure and the Venturi effect, but I'd really like to know precisely how they work as ...
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53 views

Realistic Ocean Shears

I was wondering if anyone could point me to published data on the vertical structure of strong ocean currents, such as the Gulf Stream. I am primarily interested in the mean current profile as a ...
2
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0answers
60 views

Contraction and expansion after constricting flow though a pipe

If an orifice is placed inside a pipe with a smaller diameter than the rest of the pipe, fluid will follow a curved path in order to enter the orifice, and then expand. I was wondering at what ...
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55 views

What is the relationship between complex time singularities and UV fixed points?

In this paper it is described how the turbulent kinetic energy spectrum and the flatness (a measure for intermittency) are governed by the position of the (dominant) singularities of the solutions of ...
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87 views

Shock Rarefaction Interaction

I am interested to see/know if there exist analytical solutions for shock/rarefaction interaction. A rarefaction wave catches up from behind to a shock wave. The shock will decay and the motion will ...
2
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0answers
130 views

Robot controling pouring process from a bottle

I need to solve a problem within mechanic of fluids for a part of my thesis. Robot will pick up a bottle of beer, cola, julebrus or any other kind of beverage. And then it has to bring it to the glass ...
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66 views

Seashell occurrance

Sometimes, sea shells accumulate on the sea shore, but sometimes they will instead be dragged back out to sea. What are the main physical factors that determine which of these things will happen?
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84 views

Stat mech explanation for separation of one liquid from another in gravity?

If one mixes two distinct ideal gases above the Earth's surface, one with a higher molecular mass than the other, then at equilibrium, their number density gradients will be such that at low heights, ...
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144 views

Turboshaft Turbine Mathematical Model

Are there any simplified mathematical models for how two gas coupled turbines (also called a free power turbine) should interact with one another as the speed of the driving turbine changes. (i.e.) ...
2
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296 views

How to calculate the Darcy-Weissbach friction factor for shear thinning laminar flow in a pipe?

The Darcy-Weissbach friction factor for laminar flow would be $\frac{64}{Re}$ Now, having a shear thinning (non-newtonian) fluid where the viscosity is not constant how do I arrive at $Re$? To know ...
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414 views

propeller flying physics for the layman

I'm starting a (quad?)copter build, and i can find plenty of knowledge about stabilizing the craft and things related to gyroscopy. but there's absolutely zero information on things that help me ...
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94 views

Concentration of fluid pumped through a tube?

I have a bottle filled with a fluid A, and a tube of volume $V_0$ filled with a fluid B leading away from it. When I now start pumping fluid A out of the bottle, I am interested in the concentration ...
2
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119 views

How do I simulate a constant velocity flow in porous media

I am modelling gas combustion in porous media. Most contemporary models assume that the pressure drop from the porous media is small enough to disregard, but I want to include that in my ...
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0answers
1k views

What's the meaning of a pressure coefficient in fluid mechanics?

I have a jet of air leaving a contraction from a pressurized tank at a velocity of 28.8 m/s and it's being directed towards a small object equipped with static pressure holes on its surface that give ...
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18 views

Shallow water wave question from Acheson's book

I am learning Fluid mechanics by reading Acheson's book entitled "Elementary Fluid Dynamics". Admittedly, you will need to have the book to respond to my question. I did this problem 3.1, which deals ...
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15 views

Lattice Gas Cellular Automata - HPP model square lattice

In the HPP model of LGCA, a square lattice is used and there is only one collision configuration as mentioned in figure (taken from the book Lattice Gas Cellular Automata and Lattice Boltzmann models ...
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22 views

Pressures in multiple hydraulic drive system circuits when driving common drive shaft

Assume that there are two 'idealised' and identical hydraulic drive system circuits each consisting of a connected positive displacement pump and hydraulic motor where both motors (from each ...
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0answers
28 views

Capillary action column height in a tube fitted inside another tube?

I was thinking about how would capillary action change in a tube (classic example) and in a tube fitted inside another tube (considering water as the liquid involved). Height of liquid column: ...
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23 views

Amount of fluid that moves along a path

Let suppose that $\vec{F}$ is the velocity vector field of of a fluid in space, and $\vec{s}$ is a straight path of arbitrary length. Let's suppose that $\vec{F}$ and $\vec{s}$ are parallels and point ...
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41 views

What kinds of reactions happen when bubbling air through water?

Mostly I have seen air bubbling used to remove impurities in the water itself, like exemplified in this course packet. This is called "Sparging," but I have yet to learn much about transfer between ...