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-   -   TwoPhaseEulerFoam viscosity models (http://www.cfd-online.com/Forums/openfoam-solving/58875-twophaseeulerfoam-viscosity-models.html)

 juho May 20, 2008 03:59

I compared the equations in th

I compared the equations in the source code of the Gidaspow and Syamlal viscosity models of twoPhaseEulerFoam to those presented in the Fluent 6.3 manual.

In both models the first term equals to the collisional viscosity equation in the Fluent manual multiplied by alpha.

The other terms in the Gidaspow model also equal the Gidaspow's kinetic viscosity model in the Fluent manual multiplied by alpha.

However, in the Syamlal model the rest of the terms equal the Fluent's Syamlal's kinetic viscosity model _without_ the multiplication by alpha.

Openfoam Gidaspow = Fluent 6.3 Manual ( 23.5-63 + 23.5-65 ) * alpha

Openfoam Syamlal = Fluent 6.3 Manual 23.5-63 * alpha + 23.5-64

Gidaspow:

===============================================

return rhoa*da*sqrt(Theta)*
(
(4.0/5.0)*sqr(alpha)*g0*(1.0 + e)/sqrtPi
+ (1.0/15.0)*sqrtPi*g0*(1.0 + e)*sqr(alpha)
+ (1.0/6.0)*sqrtPi*alpha
+ (10.0/96.0)*sqrtPi/((1.0 + e)*g0)

===============================================

Syamlal:

===============================================

return rhoa*da*sqrt(Theta)*
(
(4.0/5.0)*sqr(alpha)*g0*(1.0 + e)/sqrtPi
+ (1.0/15.0)*sqrtPi*g0*(1.0 + e)*(3.0*e - 1.0)*sqr(alpha)/(3.0 - e)
+ (1.0/6.0)*alpha*sqrtPi/(3.0 - e)
);

===============================================

Is there a reason for the difference or is it a bug?

 juho May 20, 2008 05:44

It's an error in the Fluent 6.

It's an error in the Fluent 6.3 manual. It has been corrected in the newest manual.

In the new manual the equations are identical to twoPhaseEulerFoam's equations.

 alberto May 20, 2008 12:31

Good :-) A.

Good :-)

A.

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