Learning Forum

[haikal.fouzi]

Hi ANSYS, I'm facing similar issue as naibaf Fluent: Problem at partition boundary in parallel simulation using VOF and porous media (ansys.com) ,where i'm trying to access c_udmi value in the exterior cell of a partition. My intention is to calculate the average value of C_UDMI for a cell_t c at thread t based on the neighboring cell (if the given cell_t c has 6 faces, that means it has 6 neighboring cells). The averaging function works if the cell zone was in the same partition, but will give the wrong value if the cell zone have more than one partition.

Below images is the correct contour of user defined memory as the cell zone is not separated by any partition.

 

Below is the wrong contour (wrong averaging calculation) as the cell zone was splitted into two different partition.

Right now, my cell x at compute node #1 couldn't get the udmi value in cell y of compute node #2 and vice versa, is there a way to access user defined memory on the exterior cell of a partition mesh so that i could get the averaging calculation right.

[Rob]

As you'll have seen in other threads, staff are little limited regarding UDF support. https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v241/en/flu_udf/flu_udf_ChapParallelUDFUsage.html  may be what you're after. 

[haikal.fouzi]

Hi Rob, thank you for the reply. I've read the parallelization chapter in the udf manual but it seems like i couldn't find a proper method to query information from the exterior cell in the neigboring compute node.

[Rob]

Will PRF_GRSUM1 do what you want? Otherwise, we'll have to rely on the wider community as there may not be a documented solution. 

[haikal.fouzi]

Hi Rob, unfortunately PRF_GRSUM1 is not suitable for my case as the each cell averaging calculation is dependent on its neighboring cell value

[Rob]

Won't the order you do the averaging in also alter the result? 

I can't assist further on this as staff are not permitted to share "specialist" knowledge. 

[haikal.fouzi]

the averaging order will not influence the result in the interior cells as the calculation is based on the pre-calculated UDM value in the boundary cells.

Below is the visualization of the averaging of interior cells based on udm value at 2 boundaries. As you can see the contour across the interior cells is pretty similar with the boundary cells.