Learning Forum

[nickgaoda]

I want to calculate the time dependent velocity gradient (G) based on the turbulent kinetic energy and dissipation rate, but I am not sure how to call values of turbulent kinetic energy and dissipation rate from prior time step. From the UDF manual, only the density, velocity, temperature and species mass fraction from previous time step can be called by the macro. Is there anyone knows how to solve it? Thank you.

[Karthik R]

Hello,

C_K(c,t) - turb. kinetic energy

C_D(c,t) - turb. kinetic energy dissipation rate

I have attached a screenshot from the Fluent customization manual. I hope this helps.

Best,

Karthik

[nickgaoda]

Hi Kremella,

Thank you for your reply. Do you mean that I can use the C_K(c,t) and C_D(c,t) directly in every time step? For some other parameters, shown below, they have the Macro (C_X_M1(c,t)) to call the previous time step.

[Karthik R]

Hello You can use DEFINE_ADJUST macro, which is executed at the beginning of each time-step. If you are storing values using C_D(c,t) into a UDM, it would read the cell values which are from previous time-step.
Hope this helps.
Best Regards Karthik

[nickgaoda]

That works! Thanks your very much