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Questions tagged [rheology]

In the context of liquids and soft matter, rheology aims to relate stresses with rate of change of strain or strain rates in a continuum-mechanics setting.

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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 ...
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Viscous fluid equivalent of hyperelasticity

A hyperelastic solid is defined as one for which the stress tensor $\sigma$ can be written as the derivative of some stored energy function $W$ w.r.t. the strain $\varepsilon$: $\sigma = \frac{\...
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Derivation of the upper convected time derivative

I read on wikipedia theat the upper convected time derivatvie is the rate of change of some tensor property of a small parcelof fluid that is written in the coordinate system rotating and stretching ...
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What is the pressure difference between capillaries and the outside air?

Why exactly do we bleed? There is a pressure gradient that causes the blood to flow from the capillaries to the outside of the skin. What is this pressure difference? The pressure inside the ...
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90 views

necessary and sufficient conditions for linear elasticity

If it's experimentally observed that a particular elastic isotropic material has a linear relationship between stress and strain for a certain range of stresses and strains, does it follow that a ...
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322 views

Objective time derivative that is not a Lie derivative

Summary Led by an interest into the concept of "Material Objectivity", I am asking myself: Are there objective time rates that are not Lie derivatives? The long read I am trying to understand the ...
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Difference in viscosity-concentration and reduced viscosity-concentration graphs

I prepared 3 different polymer solutions with varying concentration of 100, 50 and 25 ppm in order to measure their viscosity . When I plot concentration vs viscosity graph in the excel, I have a ...
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physical significance of the 'time of relaxation ' and 'time of observation'

Deborah number (used frequently in rheology) is defined as the ratio of the time of observation to the time of relaxation. In his article The Deborah Number, M. Reiner the man who coined the term has ...
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What is the short time limit of Maxwell viscoelastic fluids?

The Maxwell model for viscoelastic fluids writes: $$ \tau\stackrel{\triangledown}{\sigma}+\sigma=2\eta D(v) $$ where $D(v) = \frac{1}{2}(\nabla v +\nabla v^T)$, $v$ velocity and $\sigma$ stress tensor ...