Viscosity Definition and 254 Threads

Hello, After Favre averaging the momentum equation for an inviscid flow, the following can be obtained: $$\frac{\partial}{\partial t} \left(\overline{\rho}\tilde{u}_i \right) + \frac{\partial}{\partial x_j}\left( \overline{\rho}\tilde{u}_i \tilde{u}_j \right) + \frac{\partial...

If we have a bottle with a fluid A of X density, and in the bottom of this bottle it magically spawns the same amount of fluid B with X/2 density, fluid B should rise in fluid A until they both change positions and fluid B floats in A. Wich property of the fluids are the ones that determinates...

Hello everyone. I have a question about the sodium alginate (NaC6H7O6)n. Recently, sodium alginate is widely used for fabricating edible bottle. And I also try to utilize sodium alginate for controlling the viscosity of water. I found that with small amount of sodium alginate powder in DI water...

Homework Statement Hi, I am doing physics lab on finding coefficient viscosity of fluids and how it changes by temperature by dropping a marble into fluids, finding terminal velocity, then using stoke's law to find viscosity. (using density of fluid, sphere, sphere diameter etc). The equation...

Homework Statement [/B] A small steel-bearing falls 25.0 cm in glycerol in 23.8 s and the same distance in castor oil in 15.1 s. The densities are for glycerol 1260 kg m−3 , for castor oil 961 kg m−3 , and for steel 7830 kg m−3 . The viscosity for glycerol is 1.490 Pa s. Calculate the viscosity...

hilbert2 submitted a new PF Insights post Damped Motion in Classical and Quantum Mechanics Continue reading the Original PF Insights Post.

I'm starting the extended essay and have decided to explore more on finding the viscosity of Newtonian liquids. However I was told by my supervisor that this topic is too broad, and that I should come up with a more specific topic/research question— one that possibly relates to a real life...

I am looking for a derivation of the following formula $$ \eta=\lim_{\omega\rightarrow0} \frac{1}{2\omega}\int dt dx\langle[T_{xy}(t,x),T_{xy}(0,0)]\rangle, $$ where $T_{xy}$ is a component of the stress-energy tensor. This is claimed in for instance https://arxiv.org/pdf/hep-th/0405231.pdf...

First time post, I appreciate any advice! I own a small manufacturing company that makes RF connectors and adapters. Our automated machinery makes the connector bodies out of brass, and many of the parts we make have fairly delicate threads or features that are easily damaged when one part...

1. piston having a diameter of D = 5.48 in. and a length of L = 9.50 in. slides downward with a velocity V through a vertical pipe. The downward motion is resisted by an oil film between the piston and the pipe wall. The film thickness is δ = 0.002 in., and the cylinder weighs W = 0.5 lb...

Understanding Absolute Viscosity - shearing stress Hi everyone, I have found information about Absolute viscosity: Coefficient of absolute viscosity is a measure of internal resistance. Dynamic (absolute) viscosity is the tangential force per unit area required to move one horizontal plane...

If the single phase flows on the inclined surface and this phase (let's say water) is wetting the surface then closest layer to the surface will be bounded and will not move. And velocity of flow will be in inverse proportion with viscosity of the fluid. If now the second phase is introduced...

[moderator's note: I've decided to allow this question despite the lack of the formatting template - gneill] ladies and gentlemen, my most cordial greeting to you. i write here cause i need a viscosity vs Temperature data table about liquid metals (more specific pure Post-transition metal...

It seems that both the capillary number and the Laplace number represents the relative effect of viscous forces and surface tension. Can anybody explain the difference between them? Thanks a lot. I have attach the Wikipedia- links to these two concepts...

Homework Statement I do not need to solve this problem, see below. EXAMPLE 7.1 Air at a pressure of 6kN/m2 and a temperature of 300C flows with a velocity of 10m/s over a flat plate 0.5m long. Estimate the cooling rate per unit width of the plate needed to maintain it at a surface temperature of...

Homework Statement I have a block of mass m on a horizontal surface, which is covered in oil. The tell me the viscous resistance force is a function of the velocity, F(v)=-cv1/2, where I am assuming c is a constant of some kind. I need to find the time that it will take for the block to stop...

I am studying an inviscid fluid. I am trying to characterise the fluid. Does it make sense to call it Newtonian or should I avoid this designation? What I mean is - if there are no viscous stresses then does it make sense to characterise it's response to viscous stresses? (That box that doesn't...

Homework Statement A tank contains an incompressible liquid of density ##\rho = 1. 4\cdot10^{3}kg / m^3 ## and viscosity ##\eta=1. 4\cdot10^{-3} Pa\cdot s##. The tank is open at the summit and the level of the liquid is kept constant through a sink. At the base of the tank there is a circular...

Hello, I am currently working on a project which involves compressing air at high pressures and temperatures. I spent hours having a look for a pressure and temperature dependent equation for the dynamic viscosity of air but the only ones I could find were all temperature dependent only, such...

Hi I am trying to understand what forces are at work to slow a liquid flowing in a circular pipe As an example the above torus pipe fully filled with an incompressible low viscosity liquid. This is rotated until the fluid achieves solid body rotation and then the pipe is suddenly stopped...

Homework Statement Two identical balls A and B are dropped from rest into a tall column of viscous liquid. Ball A is dropped from the surface of the liquid while ball B is dropped from a small height ##h## above the liquid. Let ##E_A## and ##E_B## be the loss in mechanical energy of bal A and B...

I am trying to determine which fluid to use in an experiment. An important aspect of the experiment is the ratio of inertial forces (due to mass) vs the viscous forces that the fluid will experience Amongst common liquids the lowest I can see is Acetone with a kinematic viscosity of 0.41 cSt...

I am conducting an experiment that rotates a sealed donut cylinder to investigate amongst other things the inertia of the contained fluid. Process I rotate the cylinder to a set speed (assuming that the viscosity of the internal fluid will end up rotating the fluid to solid body rotation) then...

Homework Statement [/B] For many liquids the viscosity is strongly dependent on temperature. Use the table below to estimate the required maximum temperature of crude oil to flow at a rate of 4Kg s-1 through a 0.3 metre diameter pipe whilst maintaining a laminar flow. In the table it has in...

In a demonstration of the qualities of liquid Helium in type 1, and type 2 the fact that a super-fluid can permeate through capillaries which are too small for type 1 Helium to pass through. I was wondering about the equation which determines the capillary radius threshold under which the...

Hi there, I have recently been experimenting with solid metal spheres being let to fall through fluids of different viscosities and have recently been introduced to the 'Ladenburg correction'. This correction multiplies the measured velocity of the sphere to obtain the 'correct' velocity used...

Homework Statement I was told that kinematic viscosity depends on pressure , but not dynamic viscosity Homework EquationsThe Attempt at a Solution in my opinion, the dynamic viscosity depends on pressure , since it's formula is μ = tau / (du/dy) , where tau is the stress . and stress can be...

Homework Statement why the alternative formula of viscosity not = (mass x length ) / ( time x area) ? for force x time , we would get (mass x length ) / time ... Homework EquationsThe Attempt at a Solution

Hi, I read that an ideal fluid needs to be frictionless and incompressible. Please explain why, especially the incompressible part? Thanks

Hello there Physics Forum! This is my first post here. This problem has been boggling me all day and I'm need of help in piecing together what I've come up with so far. I'm currently working on a personal project related to paint spraying. In this project I'm using a syringe & needle to feed...

Hi, it's my first post. When a golf ball and a bowling ball get dropped from the same height. They will both hit the same hit the ground at the same time. But when you drop a ball with radius R and another ball eith radius 2R inside a cylinder with oil then the ball with the biggest radius...

I'm trying to understand how the Navier-Stokes equations are derived and having trouble understanding how the strain rates are related to shear stresses in three dimensions, what a lot of texts refer to as the 'Stokes relations'...

I was going through a worked example in book "Concepts in Thermal Physics" by S.J. Blundell and K.M.Blundell. The example talks about measuring viscosity of a gas between two coaxial cylinders. Homework Statement Two vertical coaxial cylinders. Outer cylinders is rotated by a motor at constant...

I know that When there is increase in temperature the molecules in a viscious liquid move further apart and this decreases the viscosity of the fluid. So does that mean the molecules are far apart in case of liquid and these molecules move further apart with increase in temperature. So a...

Hello, we were given a project in class to determine the viscosity of the egg yolk without breaking it. That is the exact question given to us. I researched and the only thing I found is that I should spin the egg to determine the viscosity. I have a tray of eggs and I just spun it and timed how...

Homework Statement Blood supply to the heart occurs through coronary arteries. Consider one of the arteries to be 2.5 mm in diameter and 3 cm in length. The average velocity of blood flow through that artery is 1.5 cm/s. Assuming the density of blood to be 1.056 g/cc and viscosity to be 3 cP...

If I were to drop a ball down a fluid with high viscosity, the ball decelerates over time and then reaches close to terminal velocity. How does displacement and velocity relates with time in terms of mathematical equation? Am I right to say: v(t) = Vterminal(1 - exp(-bt)) d(t) = Vterminal*t(1 -...

Have you ever tried to eat honey that has been in the refrigerator - hopeless huh? Both the viscosity and the density of honey change with temperature and water content and I'm told the viscosity and temperature follow a inverse cube relationship. Honey is mostly sugar (glucose/fructose and...

Hello! I am not sure if this is the right forum to post this in, but I am trying to come up with an equation to predict the viscosity of a waterborne paint after it has been reduced 10% with DI water. The following viscosities were measured at 20*C on a Ford #4 cup, units are in seconds. The...

There is a theory that space is viscous and that matter or energy traveling through it looses a very small part of its energy through this viscosity. It seems that the red shift that has been taken to be the main evidence for an expanding universe could potentially be explained by this...

Hi! I'm a bit confused about the source of drag in a 2D flow (actually I'm talking about air). I heard that if the viscosity of a fluid is 0 then there is no drag at all (no pressure and no friction drag). I think I understand why viscosity affects friction drag, but why does it have an effect...

I was watching a lecture in which the professor derived the Navier Stokes Equations for const density and viscosity. He however skipped a step and directly went from one equation to another without giving any explanation. I have attached an image file in which the 2nd equation is derived from...

Homework Statement Water flows at 0.25 L/s through a 9.0-m-long garden hose 2.0 cm in diameter that is lying flat on the ground. The temperature of the water is 20 ∘C. What is the gauge pressure of the water where it enters the hose? Side question: does the velocity of the water flow need to...

http://arxiv.org/abs/1409.4918 Abstract: We examine the cosmological consequences of an alternative to the standard expression for bulk viscosity, one which was proposed to avoid the propagation of superluminal signals without the necessity of extending the space of variables of the theory. The...

When you look at a viscous fluid its so thick and it seams that its dense and a runny fluid seams less dense. Like if you take a bottle of syrup it fells a bit heavier than a bottle of water. Plus if the atom are packed closer to each other (and in the form of liquid the atoms move past each...

Homework Statement if we have only a measuring cylinder (500mm high and 50mm diameter), a stop-watch, a ruler and a 100μL syringe. We assume that the density of the suspension is 1g/cm3, and that the polymers are spherical How can we determine the viscosity and the volume fraction of the...

I made a simple diagram. My question is, in the picture, can the hydraulic resistance of the tube connecting the fluid to the vacuum chamber prevent boiling of the fluid until it reaches the nozzle?

I am trying to understand the no slip condition (parallel velocity =0) in the presence of a permeable surface (in this case a Reverse Osmosis filter mesh ). Does the presence of permeability affect the no slip condition ? Intuitively For a gas Where viscous effects are dominated by momentum...

I don't understand units associated with kinematic viscosity. Let's recap dynamic viscosity (η): η = Shear stress (τ) / rate of shear strain (m/s)/m) η = F/A / (velocity (m/s) / gap distance (m)) η = Force( N) / Area (m2) / (velocity (m/s) / gap distance (m)) Stress (F/A) is pressure...

Homework Statement A falling sphere viscometer measures the viscosity of a liquid from the terminal velocity of a tiny, falling sphere. One such device determines that a tiny sphere of radius 46 μm falls through a liquid with a terminal velocity of 2.5 mm/s. If the density of the sphere is 4171...