The Stack Overflow podcast is back! Listen to an interview with our new CEO.

Questions tagged [viscosity]

The tag has no usage guidance.

334 questions
Filter by
Sorted by
Tagged with
12 views

Is Coefficient of viscosity frame dependent? Why/Why not?

Is Coefficient of viscosity frame dependent? Why/Why not?
23 views

What is the drag coefficient of a tetrahedron? [on hold]

I would like to know the drag coefficients of all of the Platonic Solids. However, I am more interested in that of the tetrahedron.
43 views

Does the viscosity of oil increase with rising temperature?

In order to calculate the viscosity index of a lubricant, apparently you need two input parameters. The kinematic viscosity (mm²/s) at 40°C and at 100°C. If I got it right, mm²/s means the distance ...
37 views

Shear viscosity in an acoustic plane wave

In the absence of bulk viscosity, $\eta_b = 0$, in Landau and Lifshitz book and many other places, the viscous stress tensor is defined as: \begin{equation} \sigma'_{ik} = \eta_s\left(\frac{\partial ...
44 views

About stoke 's formula

Why does the acceleration decrease whereas velocity increase for a freely falling spherical body inside a viscous liquid
84 views

Bernoulli's law for turbulent flow

Is Bernoulli's law valid for turbulent flow for a non-viscous, non-compressible, non-rotating fluid with isoentropic flow? An ideal fluid has coeffieicent of viscosity=0,which implies that it's ...
29 views

Modal filtering with Vandermonde matrix - Artificial viscosity

I am trying to implement a 2D shock detector for an artificial viscosity model to control strong nonlinearities in compressible fluids. The method I am relying on is originally from: Yu, M. L., ...
33 views

What is the theoretical flow rate of water through a tube leaving a container?

The question comes from this image: There is a container with $h$ amount of water above a hole of diameter $r$. This hole leads to a tube that the water exits through. Using the pressure on both ...
12 views

Viscous forceand it's relation with velocity gradient

How is viscous force directly proportional to velocity gradient??,lyk if consider a layer of water that is near the ground say 1st layer and a layer of water that is above 1st layer,if the velocity ...
40 views

External force in the Navier-Stokes momentum equation

The Navier-Stokes momentum equation is $$\rho\frac{\partial \bf{v}}{\partial t}+\rho(\bf{v} \cdot \nabla\bf{v})=-\nabla P + \nabla\cdot \bf{\tau} +\bf f$$ where $\tau$ is the deviatoric stress ...
44 views

Derivation of Stokes Formula using stream function

I need help with derivation of Stokes Formula. I have found derivation on Wikipedia (https://en.wikipedia.org/wiki/Stokes%27_law), but I don’t know how can I get from equation (1) to equation (2). How ...
61 views

Why doesn't mercury flow in the thermometer?

Nowadays digital thermometers are used, but in the past mercury based thermometers were used. From my experience the mercury does not flow in the thermometer tube. Mercury is a liquid, so it must have ...
51 views

How does viscous heating arise?

Viscosity arise because of fluid deformation, which causes shear within it. Momentum is then diffused down the velocity gradient. What I can't seem to understand, is how the heating arises. I'm not ...
24 views

What is the reason for the presence of a developing region in a boundary layer?

Why does a fluid first flow as shown in the entrance region before flowing as shown in the developed region ? In other words, why wouldn't it flow in developed region from the beginning ?
28 views

Bird Transport Phenomena

in the book " transport phenomena" (Bird) when obtaining the famous equation of hagen poiseuille Bird defines a variable that involves the pressure, but when doing an exercise a term magically ...
48 views

Why do we consider the viscous force to be tangential?

Is it that since it is a friction force, it needs to be tangential as other friction forces like kinetic friction and static friction forces are?
31 views

Is it possible to find the exact value of the dynamic viscosity of a fluid by applying Stokes' law?

I am a high school student who is investigating the dynamic viscosity of a fluid. Typically, high school physics model the dropping of a spherical object vertically into a viscous fluid with the ...
115 views

Can the flow be irrotational if the viscous forces act on fluid?

I tried to answer the question only using the definitions and the Navier-Stokes equation: $$\rho \frac{Dv}{Dt} = -\nabla P +\rho g -\mu[\nabla \times(\nabla \times v)]$$ In my opinion if the ...
21 views

A viscous liquid moving from different holes

Say, we have bottled viscous liquid - such as a dishwashing liquid. There are two different caps for the bottle. One with a smaller hole, one with slightly bigger hole. Both holes are very small ...
55 views

18 views

Scaling law or order estimation for turbulent viscosity in a rectangular cavity

Is there any recognized scaling law for the eddy viscosity inside a rectangular cavity? Indeed, that should mean some sort of homogenized value, since the quantity is spatially dependent. I have made ...
399 views

Why is oil called more viscous than water when we slip on oil more than we do on water [duplicate]

If we were to throw some water on the floor then walk over it we may or may not slip but it wouldn't that be difficult to walk. If we repeat the same thing with oil we it would be harder to walk as me ...
100 views

Calculating Reynolds number in a water tunnel

I am trying to calculate the Reynolds number of a flow that I will be creating in a water tunnel. Reynolds number ($RE$) is given by the following where $\rho$ gives fluid density, $u$ gives velocity ...
41 views

Why bicycles' rims are bent after winter? [closed]

I've noticed that the rims of many bicycles which are parked in the street during the whole winter are heavily bent. I'm wondering what causes this deformation? Typically, this happens to rather cheap ...
38 views

Time scale for steady flow to occur in parallel disk viscometer

Hey to whomever is reading this! I'm currently trying to solve a problem given to the class in a hydrodynamics course. I have to main questions. The following describes the problem: We are ...
30 views

Small amplitudes and Stokes drag law

Why is it that on a damped harmonic oscillator or a pendulum in a fluid, the Stokes drag law in the fluid only applied to small amplitude oscillation compared to large amplitudes oscillations? Dose ...
35 views

Taylor Couette Bernoullis

Has anyone studied a Taylor-Couette flow in the presence of a varying diameter pipe. Is there any research that i can be pointed to to understand how the pressure differences develop in a purely ...
28 views

Theory or method on how to calculate the pressure needed to push a viscous fluid through a narrow slit

I need to calculate the minimum amount of pressure I need to apply to a piece of molten glass to start making it pass through a narrow slit - think 1 kg of glass and a 0.2 mm slit. At this point I ...
158 views

How to start moving in at $Re\ll1$

I find it difficult to see how something can accelerate (and therefore increase its velocity, e.g. start to move) in a $Re\ll 1$ situation. It is customary, at low Reynolds numbers, to ignore ...
23 views

Does bernoulli's principle explain the suction by an emerging air stream?

Consider flow exiting a nozzle into atmosphere, its static pressure will decrease through the nozzle as the molecules vectors align with the direction of the exit. However, as soon as it exits the ...