Learning Forum

[yf70512]

Hello all,

I am trying to modify the source term (Changing the temperature power exponent from 1 to 4) of energy equation in non-equilibrium thermal model by UDS and UDF (DEFINE_SOURCE macro). But the Fluent crashed when the code runned with the error "999999:mpt_accept:error: accept failed: No error". I think there may be two questions:
1 how to access the solid temperature in the fluid zone and fluid temperature in the solid zone?
2 how to specify the UDS Scalar as the energy source (Figure 2)?
Could anybody help with this? Thank you in advance.

Best regards,

Fan

[yf70512]

Here is my UDF：

#include "udf.h"

#define HFS_CONSTANT 1000   
#define AFS_CONSTANT 0.1    

// Fluid Source Term
DEFINE_SOURCE(Fluid_source, c, t, dS, eqn)
{
    real Tf, Ts;
    real hfs, Afs;
    real source;

    // Obtain the fluid temperature (Tf) and solid temperature (Ts)
    Tf = C_STORAGE_R(c, t, SV_T_F);   // Access fluid temperature
    Ts = C_STORAGE_R(c, t, SV_T_S);   // Access solid temperature
    
    // Calculate or use constants for hfs (heat transfer coefficient) and Afs (interfacial area density)
    hfs = HFS_CONSTANT;  // Define or calculate hfs
    Afs = AFS_CONSTANT;  // Define or calculate Afs

    // Calculate the source term using modified expression hA(Tf^4 - Ts^4)
    source = hfs * Afs * (pow(Ts, 4) - pow(Tf, 4));

    // Define the derivative of the source term with respect to Tf
    dS[eqn] = -4 * hfs * Afs * pow(Tf, 3);

    return source;  // Return the calculated source term
}

// Solid Source Term
DEFINE_SOURCE(Solid_source, c, t, dS, eqn)
{
    real Tf, Ts;
    real hfs, Afs;
    real source;

    // Obtain the fluid temperature (Tf) and solid temperature (Ts)
    Ts = C_STORAGE_R(c, t, SV_T_S);   // Access solid temperature
    Tf = C_STORAGE_R(c, t, SV_T_F);   // Access fluid temperature

    // Calculate or use constants for hfs (heat transfer coefficient) and Afs (interfacial area density)
    hfs = HFS_CONSTANT;  // Define or calculate hfs
    Afs = AFS_CONSTANT;  // Define or calculate Afs

    // Calculate the source term using modified expression hA(Ts^4 - Tf^4)
    source = hfs * Afs * (pow(Ts, 4) - pow(Tf, 4));

    // Define the derivative of the source term with respect to Ts
    dS[eqn] = 4 * hfs * Afs * pow(Ts, 3);

    return source;  // Return the calculated source term
}

I am not sure if it is right to access the  solid temperature in the fluid zone and fluid temperature in the solid zone.

[Rob]

The problem isn't so much getting the fluid temperature as seen by the solid or vice versa but that you need to link to the two cells: so some care will be needed there. 

Changing the exponent from 1 to 4 suggests radiation effects? Will this effect anything other than the front and rear (ie external surfaces) of the solid?

[yf70512]

Hi Rob,

Many thanks for your suggestions. I would like to ask how to link the two cells.

I have tried to link them by the spatial coordinate because a dual cell approach is used in  non-equilibrium thermal model.

But the same errors occured "999999:mpt_accept:error: accept failed: No error" . The code is following:

DEFINE_SOURCE(Fluid_source,c,t,dS,eqn) 

{

 

real xc[ND_ND], xcs[ND_ND];

real Tf, Ts;

real hfs = HFS_CONSTANT;  // Placeholder value for heat transfer coefficient

    real Afs = AFS_CONSTANT;    // Placeholder value for interfacial area density

    real source;

int zone_ID;

Thread *st;

cell_t sc;

Domain *domain;

// Solid_Cell_id *st;

 

// Find  the coordinate position of the centroid

C_CENTROID(xc,c,t);

 

    // Obtain fluid and solid temperatures

    Tf = C_T(c, t);  // Fluid temperature

    // Ts = C_STORAGE_R(c, t, SV_T_S);  // Solid temperature

 

 

zone_ID = THREAD_ID (t);

 

if (zone_ID == 11)

{

domain  = Get_Domain(27);

thread_loop_c(st, domain) // loop over all cell threads in the domain

{

begin_c_loop (sc,st) // loop over all cells 

{

C_CENTROID(xcs,sc,st);

if (fabs(xc[0] - xcs[0]) < 1.0e-6 && fabs(xc[1] - xcs[1]) < 1.0e-6 && fabs(xc[2] - xcs[2]) < 1.0e-6)

Ts = C_T(sc,st);

break;

}

end_c_loop (sc,st)

}

    // DEFINE_PROFILE(Ts, st, xc);

}

if (zone_ID == 14)

{

domain  = Get_Domain(33);

thread_loop_c(st, domain)

{

begin_c_loop (sc,st)

{

C_CENTROID(xcs,sc,st);

if (fabs(xc[0] - xcs[0]) < 1.0e-6 && fabs(xc[1] - xcs[1]) < 1.0e-6 && fabs(xc[2] - xcs[2]) < 1.0e-6)

Ts = C_T(sc,st);

break;

}

end_c_loop (sc,st)

}

 

}

    // DEFINE_PROFILE(Ts, st, xc);

 

    // Calculate the source term based on the modified expression

    source = hfs * Afs * (pow(Ts, 4.0) - pow(Tf, 4.0));

 

    // Set the derivative of the source term with respect to Tf

    dS[eqn] = - 4.0 * hfs * Afs * pow(Tf, 3.0);

 

    return source;

 

}

Besides, the effect (exponent from 1 to 4) in my case  only affect the heat transfer in the interface between the solid and fluid.