Hello Fluent users, I have succesfully implemented a UDS into the steady version of FLUENT 5.5. Can anyone advise me on how to use the DEFINE_UDS_UNSTEADY routine. I see that apu and su are arguments to the function but does that mean that I should modify them? The description in the manual suggests that they are automatically calculated. Does this mean overwriting C_UDSI(c,t,0)?

I consider that the source term can be adjusted every iteration but the time dependence is activated only every time-step.

My current status is that I have an "empty" routine for the unsteady scalar and I activated it from the scalar panel. It seems a little odd that all I am doing is switching on the unsteady calculation. The result of this is that the steady state run is preserved - there is nothing to provoke a change.

Any help gratefully received, Mark mark.richardson@student.umist.ac.uk

This routine is used to chnage the form of the transient term of the UDS scalar equation from the default of dthi/dt. If your pde is for dthi/dt you won't need to use it - select default method. If you want to have a transient term of say d( g * thi)/dt where g is some function (value with spatial or time dependence) then you can use this function to change how the transient term is calculated.

Search the archives since I posted an explanation on what the su and apu terms mean some months back.

Greg