[HHOS]

Hello to all,


I am trying to create a DEFINE_WALL_FUNCTIONS macro in order to change the log-law.


The standard UDF, provided with Fluent is:

DEFINE_WALL_FUNCTIONS(user_log_law, f, t, c0, t0, wf_ret, yPlus, Emod)
{

real wf_value;

switch (wf_ret)
{
     case UPLUS_LAM:
     wf_value = yPlus;
     break;

     case UPLUS_TRB:
     wf_value = log(Emod*yPlus)/KAPPA;
     break;
     
     case DUPLUS_LAM:
     wf_value = 1.0;
     break;
     
     case DUPLUS_TRB:
     wf_value = 1./(KAPPA*yPlus);
     break;

     case D2UPLUS_TRB:
     wf_value = -1./(KAPPA*yPlus*yPlus);
     break;
     
     default:
     printf("Wall function return value unavailable\n");
}
return wf_value;
}

I have been playing with the case UPLUS_TRB because the equation there is the one in the theory-guide for the u* value.


I have however noticed that the case it triggers in my calculation is also the DUPLUS_TRB.


What does that mean?? What are those different cases, other than the first two??


If you know, how did you get that information??


And finally, why is it using "yPlus" when the theory guide clearly states that the equation used for the wall function uses y* instead of y+??

Any help would be appreciated.


Thank you very much in advance.


Regards.


hhos