[ghost82]

Hi!
I'm working on coding a new cavitational model for transient cases and I don't understand one thing..In the udf I need to access variables of the previous time step, so I'm using UDMI to store density, vapor volume fraction and some other calculated variables in the udf itself.

The udf compiles successfully.
At the end of each time step I'm using a DEFINE_EXECUTE_AT_END macro to move the current value of densities from C_UDMI(c,t,2) to C_UDMI(c,t,4) and values of volume fractions from C_UDMI(c,t,3) to C_UDMI(c,t,5).
C_UDMI(c,t,4) and C_UDMI(c,t,5) are used inside udf to access values of previous time step.
The problem is that I don't undestand why the contour plots of C_UDMI(c,t,3) and secondary phase volume fraction are not the same (even if vofM is restricted to a minimum and maximum value the contour plots are totally different)...

Can somebody explain why? I can't find the error in udf..

Thanks!

#include "udf.h"
#define min_vofV 1.e-5
#define max_vofV 0.99999

DEFINE_CAVITATION_RATE(Rayleigh, c, t, p, rhoV, rhoL, mafV, p_v, cigma, f_gas, m_dot)
{
  real p_vapor = *p_v;
  real dp, vofV, vofM, timestep;
  [some code here]

  dp = p_vapor-ABS_P(p[c],op_pres);
  vofM = MIN(MAX(min_vofV, mafV[c]*C_R(c, t)/rhoV[c]), max_vofV);
  vofV = mafV[c]*C_R(c, t)/rhoV[c];
  timestep = CURRENT_TIMESTEP;

  if (dp > 0.0)
  {
    [some code here]
    C_UDMI(c,t,2) = rhoV[c];
    C_UDMI(c,t,3) = vofM;
  }
  else
  {
    [some code here]
    C_UDMI(c,t,2) = rhoV[c];
    C_UDMI(c,t,3) = vofM;

    if (vofV < min_vofV)
    {
      [some code here]
      C_UDMI(c,t,2) = rhoV[c];
      C_UDMI(c,t,3) = vofM;
    }
  }
  *m_dot = [some code here]
}

DEFINE_EXECUTE_AT_END(execute_at_end)
{
  Domain *d;
  Thread *t;
  cell_t c;
  d = Get_Domain(1);

  thread_loop_c(t,d)
  {
    begin_c_loop(c,t)
    {
      C_UDMI(c,t,0) = C_UDMI(c,t,1);
      C_UDMI(c,t,4) = C_UDMI(c,t,2);
      C_UDMI(c,t,5) = C_UDMI(c,t,3);
    }
    end_c_loop(c,t)
  }
}

I'm attaching a first image of the contour plot of vapor volume fraction and a second image of UDMI 3 (which contains vofM values).
I don't think the problem is that I'm saving UDMI values at the mixture thread level.

[ghost82]

It seems another bug in the post processing...
When I open the dat file in cfd post and plot the phase-2 volume fraction I obtain near the same (due to vofM limits) contour plot as udm-3.

Daniele

[ghost82]

[Solution]
See here why udmi and vapor volume fraction values are different:
http://www.cfd-online.com/Forums/flu...ation-udf.html