I am trying to write a UDF for Fluent 19.1, that simulates a suction and ejection flow from a piston. I am using a sinusoidal function to model this. My UDF will not allow my simulation to converge. Does my UDF look correct? My maximum Velocity Magnitude should be 1.22 m/s so I have defined the axial velocity to my UDF. I am using the UDF compiler to run my UDF. The simulation is a transient turbulent model. Am I missing anything important in the initial set-up of my model?
Thank you for your help!
/**********************************************************************
unsteady.c
UDF for specifying a transient velocity profile boundary condition
***********************************************************************/
#include "udf.h"
DEFINE_PROFILE(axial_velocity, thread, position)
{
face_t f;
real t = CURRENT_TIME;
begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = 1.22*sin(6.2831853071796.*t);
}
end_f_loop(f, thread)
}
You can use this tutorial for checking you udf program .It is the first one .
I think that your code is ok. If your UDF compiles or interpretes without errors, even if you can 't obtain convergence for each timestep check in the results if your profile agrees with values you would exxpect from your formula. If this is ok, I would recommend reducing timestep, checking your mesh or switching solver to coupled (if it is not yet on couple option).
I was able to get the UDF to work, but it only models the ejection flow and not the suction. Any suggestions?
I am running a transient simulation, with a time step of either 0.05 or 0.005 with 300 steps. I have loaded my UDF as the axial velocity for this simulation with the magnitude set to 1.22 m/s. I have attached what my residuals look like. I have the convergence condition set to 1e-6 for the residuals. I was able to get the simulation to run ejection and suction flow, but it the solution will not converge. Any suggestions?
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