October 21, 2022 at 9:51 pmMelanie ButtsSubscriber
I have a frame motion simulation of a fan, and the results seemed to get less realistic as I decreased my mesh size. Is there such a thing as overmeshing in CFD?
These results are from my finest mesh (0.001583 m on the face of the fan blades, 0.01583 for the rest of the domain)
Here are results from a medium grid (elements twice as big)Here are results from a simulation with elements 4 times as bigMore about the settings:Transient simulationViscosity model: Laminar flowZone conditions: 1200 rpm frame motionBoundary Conditions : 0 guage pressure inlet and outlet, with zero shear walls for the sidesConvergence conditions: created report definitions for torque on the fan walls and mass flow rate applied to the outlet, set to converge each time step ignore first 20 itterations and use last 20 itterationsCalculation activities: ran 300 time steps of size 0.05 s, with maximum of 50 itterations per time stepAlso, here are some stats on the quality of my meshmax skewness of finest mesh was 0.83517min orthogonal quality : 0.14128
October 24, 2022 at 11:00 amRobAnsys Employee
What tends to happen is the solution stops changing at a certain mesh resolution. As you further refine beyond a certain point you can start to pick up additional flow features.
The fine mesh looks to be resolving the fan core: ie a region in the centre with little/no flow as the hub blocks the flow. Adjust the scale and also review the velocity vectors.
November 4, 2022 at 12:12 amMelanie ButtsSubscriber
Thank you Rob!
When you say adjust the scale, do you mean continue to decrease the mesh size? And when you say review the velocity vectors, do you mean look for vortecies and/or transient behavior in the flow?
November 4, 2022 at 9:29 amRobAnsys Employee
Display scale, you're looking at a (mostly) pale blue contour. If you tighten the scale and make sure it's the same for each case it'll make comparisons easier.
November 4, 2022 at 5:23 pmMelanie ButtsSubscriber
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