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2answers
59 views

Viscosity forces and Depth of water

I was wondering if the viscosity force depends on the depth of water. I mean it is much more harder to swim in the ocean at a depth of 1km than swimming at the surface due to the viscosity forces ?
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2answers
186 views

Viscosity calculation of a rarefied gas

I am studying the rotational-translational relaxation of a diatomic gas (like oxygen) using a GPU in order to accelerate the calculations; during the calculations I get the translational temperature, ...
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2answers
216 views

Viscosity for steam in the Reynolds number

In calculating the Reynolds number for a flow of steam in a pipe, this is the general formula I am trying to use: $$Re=\frac{\rho d v}{\mu}$$ with density $\rho$, pipe diameter $d$, flow steam $v$ ...
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1answer
46 views

Would a fluid with zero viscosity reach an equilibrium

My hunch is yes, but I can't think how to prove it. An argument against this is you have a box with a divider in the middle, one side is filled up higher than the other. The divider is removed, you ...
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1answer
42 views

Is there a conclusive correlation between viscosity and surface tension?

I'm working on a project and I need to know if the viscosity effects on the surface tension or not?
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1answer
51 views

Suffocation in a granular medium

I read of a recent accident in Alberta in which three girls fell into an open bed truck carrying canola seeds and suffocated. In that situation would it have been possible to keep breathing by using ...
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1answer
33 views

Physical reason why Prandtl number is order unity for gases?

Is there a physical reason behind the fact that for gases the thermal diffusivity is on the same order of magnitude as kinematic viscosity (and as such a Prandtl number of order unity) and if so what ...
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1answer
22 views

If there was an object such as a bucket travelling through the atmosphere very fast could the air caught in it transition to a liquid?

The question came to me after thinking of the pressure waves in front of a spacecraft during re-entry. Would the pressure caused by the air being compressed cause the air to liquefy and if so at what ...
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1answer
114 views

Application of Stoke's Law

I was looking at Stoke's law and it says that you use it to calculate the drag force on a sphere passing through a fluid. Can i also use this equation to calculate the drag force on a car going ...
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1answer
29 views

Without knowing fluid density, can it be correctly determined by measuring both kinematic and dynamic viscosity directly?

Without knowing a fluid's density, can its density be correctly determined by measuring both kinematic and dynamic viscosity directly, and then dividing these values? Can one determine cStokes and ...
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1answer
27 views

How drag force relates to velocity in the air?

As you know in the formula of drag $$F=0.5 *d*A*C*v^2$$ in different velocities we have different Reynolds number. and the Reynolds number relates to coefficient of drag. my question is how can we ...
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1answer
51 views

Will there be a drag for a solid body already dragged due to reaction?

By learning Fluid Structure Interaction tutorials, I managged to simulate a 2d transient fsi simulation using Comsol fsi fully coupled module. A solid body due to motion in vertical direction ...
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1answer
217 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
49 views

Bulk and dynamic viscosity in the atmosphere

I'm studying the physics of the atmosphere but I'm struggling with the matter of viscosity (Navier-Stokes equation) for gravito-acoustic waves. From Landau-Lifschitz : $$ (T)_{ij} = -p\delta_{ij} + ...
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0answers
902 views

Derivation of the equation of motion of a viscous fluid by Landau & Lifshitz

I am trying to follow Landau and Lifshitz, from the Volume 6 (Fluid Mechanics) of the Course of Theoretical Physics, on their derivation of the momentum equation for a newtonian viscous fluid, but I ...
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0answers
13 views

percolation permeability threshold in Helium before and after lambda point transition

There's an experiment demonstrating the properties of super-fluid Helium compared to normal fluid Helium, in which the Helium is put in a jar who's bottom is porous. The super-fluid can pass through ...
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0answers
79 views

Explanation of the liquid rope coil effect

I was recently introduced to the liquid rope coil effect by this video: https://www.youtube.com/watch?v=zz5lGkDdk78 I noticed while the video mentioned the equations governing the motion, it didn't ...
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0answers
94 views

Cosmological Bulk Viscosity - is the universe a fluid?

I was trying to make heads of tails of both this paper and the press release about it. The scientists have used bulk viscosity (as opposed to shear viscosity) and popped it into a model and somehow ...
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0answers
101 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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0answers
92 views

What is the viscous force acting on a cube?

I'm aware of the viscous drag formulae to calculate the drag force acting on a moving sphere inside a viscous fluid. But how do you improve the formulae to get the force acting on a cube with side ...
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0answers
259 views

Chapman-Enskog theory for diatomic gas

I have rarefied, dilute, diatomic gas (oxygen) and I have to calculate the viscosity using the Chapman-Enskog theory; however I couldn't find anywhere the formula the allows me to do such calculation. ...
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0answers
71 views

Argument for stability of journal bearing via inertial and viscous forces?

As I understand a journal bearing, a rotor is levitated by hydraulic forces from the lubricant. While these are lots of studies on this subject, I can't manage to find a paper that coherently breaks ...
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0answers
55 views

Dissipation depending on viscosity - where am I wrong?

Accodring to this answer to an older question of mine, dissipation in a fluid in W/kg is proportional to U³/L (U characteristic speed, L Length). I was wondering why this is independent of viscosity, ...
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0answers
51 views

Can we take transport equation of imaginary quantity?

In the RANS equation we approximate the nonlinear fluctuating terms to eddy viscosity times strain rate. Then by using turbulence models like Spalart-Allmaras etc, we take the transport equation of ...
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0answers
426 views

An equivalent for the Bernoulli equation for viscous liquids

I was wondering whether there is any equation for viscous liquids (probably derived from energy and mass conservation principles) relating the pressure, rate of volume flow, area of cross section and ...
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0answers
21 views

Pendulum with Viscous and Frictional Damping

I am trying to model a pendulum with both viscous and frictional (Coulomb) damping. The problem is that the viscous damping only occurs in one direction because I am modeling a dashpot that only has ...
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0answers
9 views

Is viscosity excluded by Lorentz symmetry in spatio-temporal discreteness?

"In the case of spatio-temporal discreteness, viscosity is excluded by Lorentz symmetry". This statement is from here. Can anyone explain why this is the case? I'm looking for an intuitive way to ...
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0answers
21 views

Working Out Shaft Torque in a Stirred Tank with a Cylindrical Cavern Formation (using a non Newtonian fluid)

Here is some background to the problem (in a stirred tank): "With yield stress non-Newtonian (viscoplastic) fluids, it is possible to generate an agitated volume around the impeller, defined as a ...
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0answers
37 views

How to determine which one is dominant shear rate vs. flow rate

I have a question for the image below. Now we have a pump connecting to a votator for transferring some slurry. The pump yields a flow rate Q, and the votator yields a shear rate 𝛾. I wanna ...
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0answers
63 views

Dissipative forces and reversible processes

A book that I have contains the following lines: For a process to be reversible, the dissipative forces such as viscosity and friction should be absent. My question is why?
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0answers
19 views

Plateau–Rayleigh instability according to liquids $Ca$ number

For examining whether viscosity or surface tension dominates each other effects, we can't refer to $Re$ or $We$ numbers because they just tell us about one of them ( surface tension and viscosity ). ...
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0answers
21 views

Relation between weight and friction in fluid mechanics

In case of horizontal flow of a fluid,does its weight affect its velocity? Or just the coeffecient of viscosity is sufficient to express the increase in friction with the increase of the fluid's ...
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0answers
13 views

Visco-elastic fluid | stress/strain relationship

I'm working on a moving visco-elastic fluid with a absorption law (against frequency) that can be represented by a Zener model (Gaussian quality factor). I try to make a numerical modeling of it ...
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0answers
38 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 ...
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0answers
52 views

Superfluids (meaning, properties)

I am curious as to what a superfluid is? I have seen videos that say that they have zero viscosity, and I know that it means that there is no friction between the layers of the fluid. But what is its ...
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0answers
139 views

Maximum velocity in a viscous fluid

Situation: A viscous fluid is flowing through a tube, and the rate of ejection is x $m^3s^{-1}$ Finding the velocity of the ejected fluid would be simple enough, by dividing the rate of ejection by ...
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0answers
604 views

How to calculate the ship resistance caused by water viscosity

If there is a ship going in the sea at 50km/h, and a length of 5m, width of 2m, how do I calculate the ship resistance caused by water viscosity? in other words I want to calculate the drag Force that ...
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0answers
822 views

Shape of the “flow head” in Laminar flow in pipe

Laminar flow is a streamlined steady flow with a uniform gradient of velocity across the diameter of the pipe. I am familiar with the elementary treatment of laminar flow, like basic velocity ...
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0answers
43 views

Viscous force in a conductor

I was told that in a conductor there is a dissipative force and if Ohm's Law is valid for a component, the component has to be dissipative. I'm trying to prove it, but I have some problems. I know ...