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simpleFoam - Change physical properties of liquid

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Old   March 5, 2014, 06:06
Question simpleFoam - Change physical properties of liquid
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vut
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Hi,

I am new user of OpenFoam. I would like to ask for help in modifying the physical properties of liquid which are:

- mass density
- viscosity

Thanks in advance.

T
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Old   March 5, 2014, 06:44
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Alexey Matveichev
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Hi,

kinematic viscosity of the fluid is kept in constant/transportProperties file. Density is not actually used in simpleFoam as fluid is incompressible.
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Old   March 5, 2014, 09:34
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Thank you, Alexey, for your answer.

I am not sure but in the system of equations for RANS, we have rho (mass density of fluid) and nut (kinematic turulent viscosity), right?

May we change them somewhere in OpenFOAM?

T

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Originally Posted by alexeym View Post
Hi,

kinematic viscosity of the fluid is kept in constant/transportProperties file. Density is not actually used in simpleFoam as fluid is incompressible.
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Old   March 5, 2014, 10:28
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Quote:
Originally Posted by vut View Post
Thank you, Alexey, for your answer.

I am not sure but in the system of equations for RANS, we have rho (mass density of fluid) and nut (kinematic turulent viscosity), right?

May we change them somewhere in OpenFOAM?

T
For incompressible fluid we can divide equations by density, so there will be no density and just kinematic viscosity.

OpenFOAM uses nuEff = nu + nut, where nu is kinematic viscosity of a fluid and you change it in constant/transportProperties, nut is calculated by turbulence model and again AFAIK there is no density in equations (well, you can pass density field to the model, but there's no density field in simpleFoam) as it is non-zero constant so we again can divide equations by it.
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Old   March 6, 2014, 05:32
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OK, I understand what you mean.

Thanks for your answer.

T

Quote:
Originally Posted by alexeym View Post
For incompressible fluid we can divide equations by density, so there will be no density and just kinematic viscosity.

OpenFOAM uses nuEff = nu + nut, where nu is kinematic viscosity of a fluid and you change it in constant/transportProperties, nut is calculated by turbulence model and again AFAIK there is no density in equations (well, you can pass density field to the model, but there's no density field in simpleFoam) as it is non-zero constant so we again can divide equations by it.
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