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.

[786868082]

Hi Fan

I encountered the same issue as you: how to obtain fluid temperature and concentration in the solid zone, and how to obtain solid temperature in the fluid zone. Have you managed to resolve this?

thanks

[Rob]

From: https://innovationspace.ansys.com/forum/forums/topic/fluent-solid-fluid-data-transfer-in-non-equilibrium-model-in-porous-zone-by-udf/

 

I'm not sure about a macro, and I'm unable to discuss undocumented macros and storage variables that may be found in the /src header files. 

I'm also very limited in what I can cover that's "non-public knowledge" which includes UDFs. However, this sort of problem does allow me a little leeway on the rules. Have a look at DEFINE_ON_DEMAND to see if you can pair the cells up (ie loop over the fluid zone to find the equivalent solid cell). This may be more complicated given the parallel conditions, so also review the IF_HOST and IF_NODE terms.