The tag has no wiki summary.

learn more… | top users | synonyms

0
votes
0answers
14 views

Find parameters of blood constitutive equation

I used a viscosimeter to study the rheology of blood. I have data of viscosity, speed, shear stress and shear rate. I want to find the parameters of the constitutive equation of blood: , where ...
7
votes
2answers
122 views

Why pouring milk from a height makes a chain shape?

I have noticed a chain-like shape when milk is poured from a height into a cup. Actually the chain pattern repeats itself after some distance and again till it reaches the milk in the cup. Any ...
1
vote
1answer
108 views

Vorticity versus Viscosity

For a work project I need to revive my aerodynamics knowledge again. Can somebody help me with the distinction between vorticity and viscosity. If a flow vorticity is not equal to zero, the flow is ...
0
votes
1answer
158 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 ...
0
votes
1answer
11 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 $v$ ...
3
votes
1answer
238 views

Why viscosity is diffusive?

I'm studying fluid mechanics in more depth during my Ph. D. and there is something related with the diffusive term that has been bothering me for a long time. Looking at the convection diffusion ...
1
vote
2answers
4k views

Is water considered a substance with low friction or high friction?

Like, for example, rubber is a substance with high friction, as an object with neither high or low friction would easily stop on it, and wouldn't skid. Ice is considered an object with low friction, ...
0
votes
1answer
80 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, ...
1
vote
1answer
62 views

Dependence of streamlined flow on viscosity

My teacher told true class the following statement:- Streamlined flow is more likely for liquid with more viscosity as sturdy flow can only be achieved with slow speed. It's true that viscosity ...
10
votes
2answers
715 views

Calculating Reynolds number for a viscous droplet

I'm trying to develop a very basic scaling law/unit analysis for viscous droplet formation, and I'd like to get some rough numerical values of the Reynolds number to play with. To be specific, I'm ...
1
vote
2answers
74 views

By what mechanism is lift produced on a rotating cylinder in an inviscid flow?

I am taking some introductory fluid dynamic classes, and have become very confused by the Kutta-Joukowski theorem. One of the conclusions that can be derived by applying Kutta-Joukowski is that a ...
0
votes
0answers
37 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 ...
4
votes
3answers
96 views

Is viscosity simply “slowing down time”?

The Pitch drop experiment has pitch, a fluid with extremely high viscosity, flowing through a funnel. In 85 years, only 9 drops have fallen. Photographs of the drops, however, show an appearance just ...
4
votes
2answers
159 views

Viscous Burgers equation physical meaning

The viscous Burgers' equation: $$ q_{t}+q\:q_{x}~=~\nu\:q_{xx}, \mbox{ where } \:\:\nu >0, $$ combines the nonlinear propagation of $q(x,t)$ and the diffusion. What is this equation for? (in ...
1
vote
2answers
536 views

Gas viscosity at high pressure, high temperature

EDIT 1 PER COMMENTS I am wanting to model nitrogen gas viscosity as a function of pressure and temperature OR learn of an existing equation that models nitrogen viscosity for the pressure and ...
0
votes
3answers
103 views

Kinematic Viscosity

How would you define kinematic viscosity? What does it physically represent? Around the Internet I've found it defined as just a ratio, and that's it. I saw in an answer that I can think of it as ...
7
votes
4answers
3k views

Does irrotational imply inviscid?

Let us consider a 2D irrotational flow, such that $\nabla\times\boldsymbol u =\boldsymbol 0$. Defining the stream function such that $\boldsymbol u =\nabla\times\psi \boldsymbol n$ where $\boldsymbol ...
1
vote
0answers
23 views

Laminar flow exits an inclined tube

I am working on a problem in which viscous flow comes out from an inclined tube, forming some kind of a fountain. In the tube the fluid is Newtonian and the flow can be treated as Poiseuille flow. I ...
3
votes
0answers
38 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} + ...
0
votes
0answers
27 views

How would a network of connected springs deform when connections slip

I'm working on modeling polymer networks, and I'm stuck on the following problem. If you apply a fixed force to a bunch of firmly connected springs, sort of like this... You'd expect the network ...
1
vote
2answers
102 views

Is viscosity a function of density only?

I know viscosity is also a function of temperature, but (excluding superfluids) are there any fluids which are less viscous than fluids at lower densities? Is density the ultimate control on ...
0
votes
1answer
41 views

Where does this viscosity formula come from?

I was reading a scientific article and i came across this formula: $$\frac{\tau_{xy}}{V_{/x}} = \eta_{0}+\eta_{2}V_{/x}^{2}+\eta_{4}V_{/x}^{4} $$ which refers to the calculation of the viscosity of ...
1
vote
0answers
96 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. ...
0
votes
1answer
41 views

Viscosity and Flow

I have a system with a fairly viscous fluid, 70,000 cP. The flow is induced by applying pressure to a plunger via compressed air. The error in viscosity for this material is +- 15% which can be ...
0
votes
0answers
20 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 ...
-2
votes
1answer
93 views

What causes a spacecraft entering the atmosphere to catch fire? [closed]

What causes a spacecraft entering the atmosphere to catch fire? A) surface tension of air B) viscosity of air C) high temperature of upper atmosphere D) greater proportion of ...
0
votes
0answers
37 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 ...
4
votes
2answers
385 views

Viscosity and surface tension

Both viscosity and surface tension are dependent on the intermolecular forces between the molecules of the liquid. Supposing from this, shouldn't there be a directly proportional relationship between ...
1
vote
2answers
6k views

Determine viscosity using falling sphere (Stokes Law, Ladenburg correction)

Introduction I am trying to determine the viscosity of a fluid. Therefore, I let a sphere of known mass m and radius r fall ...
1
vote
0answers
31 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, ...
1
vote
1answer
49 views

Qualitative idea of viscosity [duplicate]

Suppose we are considering some fluid. As I currently understand, viscosity exists because of the following: supposing we draw one infinitesimal surface on the fluid, then the fluid parcels on either ...
1
vote
1answer
45 views

Say, a liquid is made to flow in a tube. Why does the layers of the liquid in contact with walls of the pipe have zero velocity?

Say, a liquid like water is made to flow in a pipe. Why does the layer of water near the walls of the pipe have zero velocity? Does that mean that the layer of water near the pipe is stationary and ...
0
votes
1answer
63 views

Which moves faster in a time $t$: $A$ or $B$? [closed]

Suppose we have two objects, $A$ and $B$, both made of the same substance. They also have the same shape (e.g. two spheres), but $A$ is larger and therefore more massive than $B$. Both $A$ and $B$ ...
1
vote
0answers
46 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 ...
2
votes
3answers
51 views

Airway resistance greatest in tertiary bronchi

As the title reads, why is airway resistance greatest in tertiary bronchi? Primary and secondary bronchi have a lower surface area than tertiary bronchi so what makes resistance greatest at this ...
3
votes
0answers
147 views

Explicit form of the entropy production in hydrodynamics

I'm trying to understand how hydrodynamics arise from a precise, mathematical formulation of thermodynamics, learning mostly from Landau's "Hydrodynamics". So Landau starts from formulating the ...
6
votes
1answer
2k views

Is there an analytical solution for fluid flow in a square duct?

I couldn't find one but assumed it must exist. Tried to find it on the back of an envelope, but got to an ugly differential equation I can't solve. I'm assuming a square duct of infinite length, ...
0
votes
0answers
123 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 ...
4
votes
1answer
345 views

Velocity of a viscous fluid through a tube

When a viscous liquid flows through a tube in a laminar flow, why is its velocity highest at the center? I understand the concept of shear viscosity and why the liquid in contact with moving plate ...
4
votes
3answers
166 views

Why does the tea in the middle of the cup spin faster when I stir it?

Try this: Make a cup of tea, add sugar, and stir it. Now add some milk, while it's still spinning. What I noticed is that the milk appears to move around a lot quicker in the middle of the cup of ...
6
votes
1answer
1k views

What is a Physically Accurate Explanation for the Kutta Condition?

Countless arguments between highly intelligent people have been waged (on this very site in fact) as to exactly how lift can be explained in an experimentally and mathematically rigorous way. Taking ...
2
votes
0answers
329 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 ...
7
votes
3answers
335 views

How is viscosity described on the molecular level?

What is the 'molecular' origin of the viscosity? The molecular origin of elasticity is almost clear for me: at the very bottom the 'elasticity' comes from the attraction and repulsion between atoms ...
1
vote
2answers
110 views

How can a gas support tensile stresses?

In working through a rigorous derivation of the compressible Navier-Stokes equations, I find that the momentum flux in the X-direction should be driven not only by the normal pressure gradient ...
4
votes
1answer
198 views

Is a non-Newtonian gas possible?

I was wondering if it was possible to have a Non-Newtonian Gas. I was planning a science fair experiment to try to create one if its possible.
5
votes
1answer
94 views

Irrotational fluid

Often, when threating some problem of fluid dynamics I have read that people make the approximation of irrotational fluid, i.e. the velocity field is assumed irrotational: $$ \nabla \times \vec{v}=0 ...
2
votes
1answer
108 views

Torque required to turn the inside of a drum (Honey extractor) [closed]

I need to mount a motor with a variable speed drive(VSD) onto a honey extractor but need to know how much torque I need to start the extractor to start turning. The diameter is 700mm and the max ...
0
votes
1answer
105 views

What is the relationship between Q-Factor and viscosity for a Newtonian fluid based damper?

I am working with a rotary damper (paddle hanging off a shaft attached to the bottom of a rotary table and into a vat of fluid). I know the viscosity of the current Newtonian fluid, I know the flow is ...
3
votes
1answer
46 views

Deborah Number for harmonic excitation

I think I do not understand well the concept of Deborah number. It is presented in the sources available to me as the ratio between the relaxation time of a fluid and a characteristic time scale of ...
4
votes
2answers
264 views

Why do some beverages stay cold longer than others?

For my daughter's science experiment, she placed six beverages (cola, diet cola, milk, chocolate milk, apple juice, and water) in the exact same amount in the exact same type and size of plastic cups, ...