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-   -   Defining a variable Viscosity ?? (https://www.cfd-online.com/Forums/cfx/25959-defining-variable-viscosity.html)

MAB June 17, 2008 04:41

Defining a variable Viscosity ??
 
Any idea of how to define viscosity of water to be a funcions of x coordinate? I want to increase the viscosity after a specified distance in horizontal direction. Any suggestion 'll be appreciated. Thanking in advance. MAB

Rogerio Fernandes Brito June 18, 2008 18:08

Re: Defining a variable Viscosity ??
 
do you want to know how to make the expression or what expression to use?

For example: dynamic viscosity as a function of x coordinate times 2.

ownvisc(X)

A = 1.0 [Pa s] B = 1.0 [m]

ownvisc=(A*(2*(X/B)))

Make a CEL expression and edit this material on what you are working in!


MAB June 19, 2008 06:32

Re: Defining a variable Viscosity ??
 
Thanks Rogerio F.B. i will try this. what i exactly want is to increase the viscosity of water by 10 times after say x=20m where as total length along x-axis is 30m. i have tried it usin step function as step((x-20)/1m)*10*viscwater + actual viscosity of water but the solver didn't run ..each time it gave an error. any suggestion

CycLone June 19, 2008 10:06

Re: Defining a variable Viscosity ??
 
The solver will not allow the viscosity to change based on spatial coordinates make sense physically.

What are you physically trying to model? Why is the water viscosity changing at all?

-CycLone

MAB June 20, 2008 05:45

Re: Defining a variable Viscosity ??
 
Hi CycLone, I am modelling water waves on free surface. neer outlet i want to increase the viscosity of water so that the waves gets damped before approching the outlet, i want to do this to avoid refelection. (it has been easily done in starccm+) any further suggestion?(

Jesse July 10, 2008 08:14

Re: Defining a variable Viscosity ??
 
step((x/1[m]-20)*10*viscwater+actual visosity of water


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