Sharp variation due to mesh

saeed jamshidi · August 21, 2023, 12:08

Hi,
I have simulated flow over cylinder in Re=200 in openfoam, and I have used snappyHexMesh, but it looks there are sharp variations in velocity field in the regions that mesh switches from one level to another.
I have attached my mesh and velocity contour for your consideration.
I know here is Ansys Fluent forum, but I hope you could helpe me on the basis of your experience in fluid mechanics.
Thanks in advance.

CFDKareem · August 21, 2023, 15:19

The change in mesh elements is too abrupt. You will need a more gradual transition from the larger elements to the small ones. Sharp changes in mesh size can lead to numerical error, which you are seeing in your simulation.

I am unsure of how to do this in Openfoam, but in Fluent you can use a "Growth Rate" which will smooth the transition between cells of varying size.

August 21, 2023, 15:19		#2
CFDKareem Senior Member Kareem Join Date: Nov 2022 Location: New York Posts: 157 Rep Power: 6	The change in mesh elements is too abrupt. You will need a more gradual transition from the larger elements to the small ones. Sharp changes in mesh size can lead to numerical error, which you are seeing in your simulation. I am unsure of how to do this in Openfoam, but in Fluent you can use a "Growth Rate" which will smooth the transition between cells of varying size. saeed jamshidi likes this. __________________ Please like the answer if it helped! Video Tutorials and Tips: https://www.youtube.com/@cfdkareem/featured

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