UDF for electric flux in diffusion

Achini · March 27, 2021, 03:49

Hello!

I am trying to simulate the diffusion of nanoparticles under an electric field.
There are both diffusion flux and electric flux.
My objective is to model this as a homogeneous mixture, considering the effect of the electrostatic force on each nanoparticle flux.

𝐽 = −D 𝜕𝐶/𝜕𝑥 + (𝑣_𝑒𝑚 + 𝑣_𝑒𝑜 )𝐶

where,
𝑣_𝑒𝑚 = electro migration velocity
𝑣_𝑒𝑜 = 𝑒𝑙𝑒𝑐𝑡𝑟𝑜 𝑜𝑠𝑚𝑜𝑠𝑖𝑠 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
C = concentration

I am planning to use fluent species transport model with a UDF to add the flux due to the electrostatic field ( the part indicated in red colour).

Can someone please help me with this?
What is the macro I should use to define the electrostatic flux?

Please help!
Thank you.

Yasser · April 2, 2021, 22:42

Use DEFINE_SOURCE

Achini · April 25, 2021, 02:30

Hello Yasser,

Thank you for your reply.
I wrote the following code to add the term mentioned above.

#include "udf.h"
#include "mem.h"

Thread *t;
cell_t c;
face_t f;

DEFINE_SOURCE(electrostatic_flux,c,t,dS,eqn)
{

real source,x,d,v,con;

x = C_YI(c,t,0); /* Species mass fraction */

d = C_R(c,t);

con = x*(d/104);

v = 17.6131*pow(10,(-10));

source = con*v;

return source;

}

This code compiles and runs without any error.
But I haven't added the dS
term which is defined for source terms macro in UDF manual.

Can someone please tell me whether it is necessary to add the dS term for source terms macro?

Thank you!

March 27, 2021, 03:49	UDF for electric flux in diffusion	#1
Achini Member L.A.Isanka Join Date: Jul 2020 Posts: 55 Rep Power: 6	Hello! I am trying to simulate the diffusion of nanoparticles under an electric field. There are both diffusion flux and electric flux. My objective is to model this as a homogeneous mixture, considering the effect of the electrostatic force on each nanoparticle flux. 𝐽 = −D 𝜕𝐶/𝜕𝑥 + (𝑣_𝑒𝑚 + 𝑣_𝑒𝑜 )𝐶 where, 𝑣_𝑒𝑚 = electro migration velocity 𝑣_𝑒𝑜 = 𝑒𝑙𝑒𝑐𝑡𝑟𝑜 𝑜𝑠𝑚𝑜𝑠𝑖𝑠 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 C = concentration I am planning to use fluent species transport model with a UDF to add the flux due to the electrostatic field ( the part indicated in red colour). Can someone please help me with this? What is the macro I should use to define the electrostatic flux? Please help! Thank you.

April 2, 2021, 22:42		#2
Yasser Member Yasser Selima Join Date: Mar 2009 Location: Canada Posts: 51 Rep Power: 19	Use DEFINE_SOURCE Achini likes this.

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April 25, 2021, 02:30		#3
Achini Member L.A.Isanka Join Date: Jul 2020 Posts: 55 Rep Power: 6	Hello Yasser, Thank you for your reply. I wrote the following code to add the term mentioned above. #include "udf.h" #include "mem.h" Thread t; cell_t c; face_t f; DEFINE_SOURCE(electrostatic_flux,c,t,dS,eqn) { real source,x,d,v,con; x = C_YI(c,t,0); / Species mass fraction / d = C_R(c,t); con = x(d/104); v = 17.6131pow(10,(-10)); source = conv; return source; } This code compiles and runs without any error. But I haven't added the dS term which is defined for source terms macro in UDF manual. Can someone please tell me whether it is necessary to add the dS term for source terms macro? Thank you!