[ndtrong]

Hi everyone,

I am trying to make an UDF function that can change timestep in unsteady simulation with Fluent.
Howeve, when I compile the UDF function with fluent, it show error like that:
..\..\src\timeStep.c(29): error C2059: syntax error: 'bad suffix on number'

The UDF file is as below:

#include "udf.h"
#include "unsteady.h"
DEFINE_DELTAT(myDeltaT, domain)
{
/*time step, flow time parameters*/
real timeStep, flowTime;
real cDeltaT;
real CFL;
real timeCheck;

/*variable to check velocity*/
real Ux, Uy, Uz, velCell;

/*variable to get minimum of volume*/
real volume;

/*common variable */
Domain *d;
Thread *t;
cell_t c;

/*Get domain*/
d = Get_Domain(1); /*Get the domain using ANSYS FLUENT utility*/

/*get timestep and flowtime*/
flowTime = RP_Get_Real("flow-time");
timeStep = RP_Get_Real("physical-time-step");

CFL = 0.1;
if(flowTime < 1.0d-5)
{
timeStep = 1.0d-6;
}
else
{
/*Loop over all cell threads in the domain*/
//minVol = 1.0d+9; /*Assign first value for minVol*/
timeCheck = 10.d0;
thread_loop_c(t,d)
{
/*Compute min cell's volume*/
begin_c_loop(c,t)
{
volume = C_VOLUME(c,t); /*get cell volume*/
Ux = C_U(c,t); /*get x component of velocity of current cell*/
Uy = C_V(c,t); /*get y component of velocity of current cell*/
Uz = C_W(c,t); /*get z component of velocity of current cell*/
velCell = sqrt(pow(Ux,2) + pow(Uy,2) + pow(Uz,2)); /*magnitude of velocity in current cell*/
cDeltaT = CFL * velCell/volume; /*compute timeStep in each cell volume*/
if(cDeltaT < timeCheck)
{
timeCheck = cDeltaT;
}
// cDeltaT = timeCheck;
}
end_c_loop(c,t)
timeStep = timeCheck;
}

Message("timestep %g \n",timeStep);
return timeStep;
/*get minimum of cell volume*/
}

}

It is appreciated if someone could explain to me the way to deal with this stuck.

I thank you very much,

[pakk]

if(flowTime < 1.0d-5)

What is 1.0d-5?
Don't you mean 1.0e-5?

[AlexanderZ]

what fluent version do you use?

[ndtrong]

Originally Posted by pakk

if(flowTime < 1.0d-5)

What is 1.0d-5?
Don't you mean 1.0e-5?

Dear Pakk

I thank you very much for your suggestion. My problem is solved.

[ndtrong]

Originally Posted by AlexanderZ

what fluent version do you use?

Dear AlexanderZ

I am using Fluent v19.2

Do you have any comments or suggestions for this?

Thanks

[AlexanderZ]

v19.2 is parallel by default

you should organize your UDF to work in parallel

flowTime = RP_Get_Real("flow-time");
timeStep = RP_Get_Real("physical-time-step");

must be read on host, than transfer to nodes

Ansys Fluent Customization manual | Parallel Considerations