Learning Forum

[sinasalahshour74]

Hello

I want to set sinusoidal value of electric potential (MHD module) for a wall, first i try expression but i faced to error :

Error: wta(2nd) to string_eq

Error Object: __expr__

 then i try Profile and UDF profile , but agian i faced to problem , when i use them it consider the wall to insulated.

Could someone help me how can i set sinusoidal value for current density ( Electric Potential MHD) ?

Best Regards,

[Rahul Mule]

Hi,

Could you please share the expession / UDF used for current density profile ?

Regards, 

Rahul

[sinasalahshour74]

Thank you for your response,

this is my UDF profile code:

#include "udf.h"

#define PI 3.141592654

 

DEFINE_PROFILE(current_density,thread,position)

{

 

face_t f;

real t = CURRENT_TIME;

 

begin_f_loop(f,thread)

{

 

F_PROFILE(f,thread,position)=13*sin((2*PI/0.04)*t);

 

end_f_loop(f,thread)

}

}

 

This is expression :

 

13*sin((2*PI/0.04[s])*Time)

 

I try Define Adjust , but it dosent work like which i want :

# include "udf.h"

 

DEFINE_ADJUST(adjust_gradient, domain)

{

int i = 13.;

Thread *t = Lookup_Thread(domain, i);

face_t f;

real tt = CURRENT_TIME;

 

begin_f_loop (f,t)

{

F_UDSI(f,t,0) = 0.02*tt;

}

end_f_loop (f,t)

}

 

Regards,

[Rahul Mule]

Hi, 

Unload the previously loaded UDF and then use expression. Better if you use latest version.

And go through the entire Fluent setup visiting each panel and make sure that the values are entered 
correct format.

Regards,

Rahul

[sinasalahshour74]

Thank you for your response,

I try expression without UDF , but when i click on MHD module this error is being shown :

Error: wta(2nd) to string_eq

Error Object: __expr__

And when i choose the wall in MHD boundary condition box this error is being shown :

Error: ASSV: invalid argument [2]: improper list

Error Object: #f

when i run the fluent , this message is being shown:

===============Message from the Cortex Process================================

Compute processes interrupted. Processing can be resumed.

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

 

Regards

[Rahul Mule]

  - wta errors often occur when a case file of a recent FLUENT version is to be loaded into an older one

 - it also occur if (in the Workbench) an incompatible network is to be loaded to a set-file

Please check which cause is likely to occur to you. 

Hope that helps you !!

Regards,

Rahul

[sinasalahshour74]

Thank you for your response

version is the same , i don't understand what do you mean about incompatible network?

Does MHD module support transient value ?, in one of Forum someone said we can't use expression and parameter for MHD module , this is true?

I ask the ANSYS Group but i havent receive answer yet.

Regards

[Rahul Mule]

Hi, 

The MHD model does not allow expressions, so the MHD model inputs were out-of-sync with the boundary conditions.

Regards,

Rahul.

[sinasalahshour74]

Dear Rahul,

Thanks, so there isn't any way to set transient value for boundary condition? like hack or special UDF

Regards,

[Rahul Mule]

Hi 

Please go through 29.3. Using the Ansys Fluent MHD Module for more information about case setup using MHD module.

Regards.

[sinasalahshour74]

Dear Rahul,

I have read this part , but i can't find the Note which about cant use expression or UDF for boundary condition in Electric Potential part , How can i make sure that we can't use transient value for boundary condition in Electric potenial part in MHD module

Regards,

[Rahul Mule]

Hi,

Please have a look at this.

Hope this helps you!!

Regards, 

Rahul

[sinasalahshour74]

Hi,

Thank you, I can't access and sign up the site you linked , i used Help Doc software 2021 and does not have this Note, Thansks.

Best Regards,