[robboflea]

Hi all,

I am working on some complicated boundary condition manipulation using UDFs and I do need a way to enforce the wall boundary conditions without initializing the solution.

To clarify, here's the workflow I am following.
1) read the case and data
2) assign wall temperature profiles from some data files

at this point I need to execute a UDF that takes those wall temperatures and stores them. The problem is that these values coming from the assigned temperature profiles, are not actually enforced on the solution unless I either start the solution itself or I initialize the solution using one of the methods (hybrid, fmg...). The issue is that I do not want to initialize the solution as it will then probably take longer to converge and I'd prefer not. I cannot either start the calculation as the CFD involves moving meshes and if I start it it's going to to to the first time-step, deforming the grid and this will not work (for reasons that deal with what this UDF is supposed to do, I won't bother you with this).

The question is: is there a way to, let's say, enforce the wall boundary conditions without initializing the solution? Or maybe initialize the solution explicitly from a data file? Bear in mind that reading the data file does not suffice as this does not enforce the wall boundary conditions as an initialization would!

Thanks a lot!

Rob

[`e`]

You could populate the boundary face values with a DEFINE_INIT or DEFINE_ON_DEMAND macro, by looping over the faces within your boundary zone. Alternatively, disable the dynamic mesh for the first time step (note: the dynamic mesh is called at the beginning of each time step).

Originally Posted by robboflea

I cannot either start the calculation as the CFD involves moving meshes and if I start it it's going to to to the first time-step, deforming the grid and this will not work (for reasons that deal with what this UDF is supposed to do, I won't bother you with this).

We are intrigued, please elaborate.

[robboflea]

Originally Posted by `e`

You could populate the boundary face values with a DEFINE_INIT or DEFINE_ON_DEMAND macro, by looping over the faces within your boundary zone. Alternatively, disable the dynamic mesh for the first time step (note: the dynamic mesh is called at the beginning of each time step).



We are intrigued, please elaborate.

Unfortunately I can only use profile files as the wall temperature I am trying to model varies from point to point in a way I cannot model through an analytical function. It then becomes a nightmare to assign values using a UDF. I think resorting to disabling the dynamic mesh is the only way I can do this. Seems a plausible way out.

The issue is that if I assign a temperature profile on a rotating wall, Fluent does not rotate the profile together with the mesh. I am writing a UDF that does so. The workflow reads like:
1) assign wall temperature on non-rotated wall using .prof file
2) call a UDF that stores for each boundary node its wall temperature
3) start the unsteady calculation so for each time-step we now have:
- rotate the mesh
- call a define profile UDF that assigns the wall temperature to the wall not based on the position but on the node ID

I was struggling on point 1). I think now it should be working based on your suggestion.

[robboflea]

by the way: do you know how to disable mesh rotation from TUI? struggling to find it...

[robboflea]

just in case anyone else needs it, the command is: p, li { white-space: pre-wrap; }

/define/boundary-conditions/modify-zones/copy-mesh-to-mrf-motion