[ANSYS Meshing] Problem in convergence due to poor mesh quality

dahiya3806 · June 11, 2019, 01:48

I am trying to simulate a ceiling fan using the sliding mesh technique. The fan is of 24-inch dia, a cylindrical rotating domain encloses the fan and enclosure(room) is 10*10*9 feet. I have tried many meshing techniques. Most of them give an error "mesh could not be generated with given input". meshing was successful using patch conforming tetrahedral but the minimum orthogonal quality is of the order of 10^-9 and maximum aspect ratio of 10^3. I am sure this is the reason for divergence error.

I have tried all the resolution of mesh and different element size, from total elements value of around 900000( min element size - 200 mm) to around 30000000 ( with min element size of 10 mm and 2 refinements at blades of fan in the rotational domain). there is a little change in the numbers of orthogonal quality and aspect ratio.

The geometry is pretty smooth and simple. don't think there should be any problem because of that.

Please Help!

jeytsav · June 14, 2019, 21:01

Hi dahiya3806,

Can you please post a picture of your geometry just to get an idea?

Best,
Ioannis

dahiya3806 · June 15, 2019, 00:53

I am able to get the orthogonal quality up to 0.015 by removing bolts and holes but that's still not good enough. The case diverged after 350 iterations (11-time steps of 0.001 sec). Should I go for an even smaller time step?
No. of elements in mesh - around 2,600,000. Rotating domain velocity - 350 RPM. I am using the K-E turbulence model.

June 11, 2019, 01:48	Problem in convergence due to poor mesh quality	#1
dahiya3806 New Member Abhishek Dahiya Join Date: Jun 2019 Posts: 2 Rep Power: 0	I am trying to simulate a ceiling fan using the sliding mesh technique. The fan is of 24-inch dia, a cylindrical rotating domain encloses the fan and enclosure(room) is 10109 feet. I have tried many meshing techniques. Most of them give an error "mesh could not be generated with given input". meshing was successful using patch conforming tetrahedral but the minimum orthogonal quality is of the order of 10^-9 and maximum aspect ratio of 10^3. I am sure this is the reason for divergence error. I have tried all the resolution of mesh and different element size, from total elements value of around 900000( min element size - 200 mm) to around 30000000 ( with min element size of 10 mm and 2 refinements at blades of fan in the rotational domain). there is a little change in the numbers of orthogonal quality and aspect ratio. The geometry is pretty smooth and simple. don't think there should be any problem because of that. Please Help!

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June 14, 2019, 21:01		#2
jeytsav Member jey Join Date: Nov 2016 Location: Greece Posts: 30 Rep Power: 10	Hi dahiya3806, Can you please post a picture of your geometry just to get an idea? Best, Ioannis

June 15, 2019, 00:53		#3
dahiya3806 New Member Abhishek Dahiya Join Date: Jun 2019 Posts: 2 Rep Power: 0	I am able to get the orthogonal quality up to 0.015 by removing bolts and holes but that's still not good enough. The case diverged after 350 iterations (11-time steps of 0.001 sec). Should I go for an even smaller time step? No. of elements in mesh - around 2,600,000. Rotating domain velocity - 350 RPM. I am using the K-E turbulence model.