Hi all, I want to write a UDF in unsteady fluent.But I have a problem with it.I want under a condition that is clear for the program ;UDF makes fluent to only change its values for CURRENT_TIME and N_TIME (i.e. the time of the program and variables).I don't realy want to revert the simulation results back to its initial values at the begining of the time step.How can I do that?

thanks in advance

Hi, It is not possible to change the time step or current time inside a UDF, if u are looking for variable time stepping, it is possible through solve->iterate panel. there is also a macro available to vary the time step size in fluent..

best wishes, Sujith

Hi thank you for your reply ,can I make fluent to reiterate the time step with the current values of variables (e.g pressure ,velocity , etc. )with in my UDF?

thanks in advance

Hi, Isn't it same as increasing the number of iterations in a time step.

i am not sure if this can be achieved through a UDF. You can try reducing the numbre of iterations N_ITER in UDF for reiterating.

best wishes, Sujith

hi Sujith, thanks a lot. i really want to do that i.e. i want to increase the number of iterations in a time step until my necessary condision is met. can you reply me how i can do that?

Hi, well i am not sure if there is any method to do that... did u try reducing N_ITER

Best regards, Sujith

Hi, thank you i don't know how can i use N_ITER for increasing the iterations when the convergence conditions of FLUENT are met.

can tou explain it to me? thanks.

I am not pretty sure of this method. u need to check this. N_ITER is the macro for the number of iterations. You can access this inside a UDF. you may need to use DEFINE_ADJUST to check the condition. if it is satisfied you can reduce the number of iterations, N_ITER so that fluent will continue the number of iterations till the specified number of iterations are done in a time step.

hope this helps

Sujith

Hi, i think we can not alter the N_ITER within a UDF. i've implemented a similar idea through N_TIME and it was not successful. also i think changing the number of iterations when the convergence conditions is met can not help.

Best wishes

amn