I observed in some manuals and websites for performing transient simulation in Fluent that UDF (sinusoidal profile of pressure) has been used at the pressure outlet of the domain. Is it necessary to use UDF instead of a constant pressure at the outlet? What are the possible scenarios where we us UDF??
Sourabh Bhardwaj : If the boundary conditions are using constant values, than obviously no UDF is necessary for conducting a transient compressible simulation (if no other physics would require a UDF).
Even for a sinusoidal pressure profile and by using ANSYS Fluent 2019.R2 or newer no UDF would be required anymore. You might want to check out the capabilities of the newly introduced expression language in Fluent, which would allow to define such a sinusoidal pressure profile without writing a UDF, but just assigning an appropriately defined expression. In ANSYS CFX expression language is an old thing, being available already for more than 17 years. But for Fluent users this came along only recently and in comparison to ANSYS CFX's CCL language the capabilities with Fluent's expressions are still a bit limited. So it depends on your final simulation goal, whether expressions will entirely solve your problem or whether you need to revert to UDF's.
Regards,
Dr. Th. Frank.
Thomas Frank The reason for using UDF at the outlet is that the unsteadiness in the solution is gradually damping and reaching a steady state value, even though the problem I am simulating is unsteady in nature. This led me to apply a UDF at the outlet as mentioned in the internet and ANSYS manual for solving compressible flow problems.
I am not sure whether not using a UDF is leading to steady state of the problem in transient simulation.
- Badges
- Science topic