UDS:Why does the scalar do not flow with the flow field？？

Huo zero · March 19, 2018, 08:48

The scalar equation does not flow with the flow field and presents the form of diffusion. The value of the monitored point has been increasing, and there is no trend to be unhange.why does this problem arise? I can't insert image, if you are interated in it , please contact me . Please~

e_cfd · March 19, 2018, 09:18

did you define the diffusion coefficient of the scalar in the fluid properly?

Huo zero · March 19, 2018, 22:09

Yes！I think I have done the right thing. And this is my UDS code. Would this be other problem?? Thanks for your reply.

#include "udf.h"

DEFINE_DIFFUSIVITY(cell_scalar_diffu, cell, thread,i)
{
real scalar_diffu; /*coefficient of scalar diffusion*/
real sigma_scalar=1.0; /*Schmidt number*/
real mu_eff; /*effecitive viscosity*/

mu_eff=C_MU_T(cell,thread);

scalar_diffu=mu_eff/sigma_scalar;

return scalar_diffu;
}

Huo zero · March 19, 2018, 22:10

Quote:

Originally Posted by e_cfd

did you define the diffusion coefficient of the scalar in the fluid properly?

Yes！I think I have done the right thing. And this is my UDS code.Thanks for your reply.

#include "udf.h"

DEFINE_DIFFUSIVITY(cell_scalar_diffu, cell, thread,i)
{
real scalar_diffu; /*coefficient of scalar diffusion*/
real sigma_scalar=1.0; /*Schmidt number*/
real mu_eff; /*effecitive viscosity*/

mu_eff=C_MU_T(cell,thread);

scalar_diffu=mu_eff/sigma_scalar;

return scalar_diffu;
}

e_cfd · March 20, 2018, 03:57

Even though I am not familiar with this definition for the diffusivity coefficient, it seems that the diffusion is dominant (diffusion coefficient is very high).

Moreover, pay attention that in uds rho*D is applied.

March 19, 2018, 08:48	UDS:Why does the scalar do not flow with the flow field？？	#1
Huo zero New Member Huo Join Date: Mar 2018 Posts: 8 Rep Power: 8	The scalar equation does not flow with the flow field and presents the form of diffusion. The value of the monitored point has been increasing, and there is no trend to be unhange.why does this problem arise? I can't insert image, if you are interated in it , please contact me . Please~

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March 19, 2018, 09:18		#2
e_cfd Member ehsan Join Date: Sep 2014 Posts: 38 Rep Power: 11	did you define the diffusion coefficient of the scalar in the fluid properly?

March 19, 2018, 22:09		#3
Huo zero New Member Huo Join Date: Mar 2018 Posts: 8 Rep Power: 8	Yes！I think I have done the right thing. And this is my UDS code. Would this be other problem?? Thanks for your reply. #include "udf.h" DEFINE_DIFFUSIVITY(cell_scalar_diffu, cell, thread,i) { real scalar_diffu; /coefficient of scalar diffusion/ real sigma_scalar=1.0; /Schmidt number/ real mu_eff; /effecitive viscosity/ mu_eff=C_MU_T(cell,thread); scalar_diffu=mu_eff/sigma_scalar; return scalar_diffu; }

March 20, 2018, 03:57		#5
e_cfd Member ehsan Join Date: Sep 2014 Posts: 38 Rep Power: 11	Even though I am not familiar with this definition for the diffusivity coefficient, it seems that the diffusion is dominant (diffusion coefficient is very high). Moreover, pay attention that in uds rho*D is applied.