UDF for Species mass fraction
 

Hi everyone! I´m solving flow in a artificial heart and need to "reset" mass fraction of a species at certain times during the simulation. I,ve written a DEFINE_ADJUST UDF for the mass fraction, C_YI. But nothing really happens in Fluent. No errors, but the UDF doesnt effect the solution.

Has someone else experienced the same?

What to do? Please help.

Re: UDF for Species mass fraction
 

Not sure what you mean by "nothing really happens in Fluent".

Have you checked that the DEFINE_ADJUST UDF runs? To check it, I would put a dummy print statement in your UDF and make sure you have it hooked up properly.

The only times I've used DEFINE_ADJUST, I've had to manually specify the thread_id to perform D_A on. (This can be found by looking at a list of boundaries and domains in Fluent).

I've used C_YI several times. I would suggest that you print the initial values of C_YI one time and then print the values of C_YI again once you have changed them in your D_A UDF. Could be that they are changed somewhere else in Fluent, especially if your "reset" doesn't physically make sense.

Re: UDF for Species mass fraction
 

I have the same problem, I need someone's help for writing the UDF. Can Daniel or Allan help me out in this? I'll be happy to talk to you guys in email. Thank you.

Re: UDF for Species mass fraction
 

Hi! I believe that define adjust would work. To reset the mass fraction, one should just loop over all threads and cells:

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

/*Loop over Thread and cell*/ C_YI(c,t,0) = 0.; /*End Thread and cell loop*/

where C_YI(c,t,0) is the species mass fraction. Since I have had other, more severe problems, I have not tried it. I get convergence problems related to the spcies transport equation. If you have any general guidelines for this I'd be happy to hear them. /Daniel I