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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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Can you use formula for viscosity derived from Stokes' law to calculate viscosity of non-Newtonian fluid if constant force is applied?

I would like to drop a ball into a test tube containing mixed corn starch and water ( in different ratios) and use Stokes law to get the viscosity for the fixed weight of the ball that I used. Would ...
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Time derivative term in Navier Stokes equation for fluid in porous media

I was reading the research paper Homogenization of peristaltic flows in piezoelectric porous media and came across the hydrodynamic equation: $$\mu \nabla^2 v^f -\underline{ \rho_f (\dot{v}^f + w \...
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Calculating shear amplitude for molecular dynamics

I’m working on a molecular dynamics simulator and want to find shear amplitude. How could do I so when particles are moving randomly? The simulation is 3d, I know some stuff about shear anplitude. I ...
Quantumidiot's user avatar
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Sense for a viscoelastic term of Maxwell type

I go reference the book of Jan Prüss (Evolutionary Integral Equations and Applications, 2012) as needed. In this book (pg. 128) it is explored some concepts of stress and strain considering the ...
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How do I quantify an adhesive's ability to stick in contrast to flow?

Let's say you glue a ball to a shovel. How do you quantify this adhesive's and ball's ability to stick to the shovel, moving at different speeds, in air and then while the shovel digs into the ground? ...
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How can you get the isotropic Young's modulus and Poisson's ratio from rheology data?

I wanted to ask on how to get the Young's modulus and Poisson's ratio for a viscoelastic biomaterial. I have rheological data from the characterization of the biomaterial, the G' and G'' (storage and ...
Tenna's user avatar
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Viscoelastic Kelvin-Voigt model and inelastic strain

In a viscoelastic medium, the total strain can be assumed as the sum of elastic strain and inelastic strain (ref1,2): \begin{align} \label{eq1} (1): \mathcal{E}^t_{ij}= \mathcal{E}^e_{ij}+\mathcal{E}^...
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Maxwell model subject to reversing constant strain rate

I've been reading about viscoelastic models and using Excel to plot some of their characteristics. I'm particularly interested in their response to a constant strain rate which reverses periodically ...
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Can an electrorheological non-Newtonian fluid be in a definite shape for a short time?

I have seen this Experiment: ELECTRORHEOLOGICAL FLUIDS and balloon Experiment (Stops flow with Static Electricity), and have seen that simple cornstarch is affected by electrostatic forces. The ...
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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 ...
alonoid's user avatar
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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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Why is shear stress equal to half of yield stress?

Why is the value for acceptable shear stress equals to half of yield stress? $$ \tau = \frac{\sigma_{yield}}{2} $$ P.s Along the math behind it would be possible to explain this with visual consepts?
Jek Denys's user avatar
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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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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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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 ...
Thomson1's user avatar
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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 ...
Thomson1's user avatar
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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 ...
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