Meshing VAWT – Very high skewness

[mohalinasre2001]

Hello Everyone,

I am currently working on my master's thesis, and I have been struggling with mesh quality for some time now. I have realised that decreasing the element sizes isn't helpful, as I have reached over 40 million elements and the skewness is still very high (0.99) for few elements (7e-4 %). The orthogonal quality is also low for 4.1e-5 % of the elements. This is a low percentage but still these elements can cause problems in my runs.

The geometry consists of a VAWT with tip sails attached to both ends of the blade. Inflation layers are added to both the blade and the tip sails.

I will attach images of the mesh showing the mesh settings on the side along with the mesh quality worksheet.

You can also find below an image showing the bad quality cells located near the inflation layers of the blades and the tip sails.

I would appreciate if anyone has a solution to this problem! Thank you in advance!!

[mohalinasre2001]

I forgot to mention that once I supressed the inflation layers, the quality turned almost perfect. So I am sure the problem is in these layers, but I am not sure how to toggle this problem.

[rademacherdacostacabral.v]

I am not too familiar with the Ansys Mehser. Do you have access to the Fluent Mesher? If so you could try to use it and see if it yields a better quality mesh.

Perhaps the Ansys Mesher prioritizes the inflation layer to a point where it can't create reasonable quality cells anymore. I know from working in Fluent Mesher that the inflation layer is "collapsed" when the gaps are too small or the corner angles too sharp. In that case you might see Stair Stepping and larger cells at the boundary. While that is not great it is probably better than highly skewed cells. You can then run your simulation and check the Y+ value to see if the mesh is still fine enough for your application. 

[Essence]

Hello,

Yes, please try uisng Fluent mesher instead of Ansys mesher, since the former has more features than the latter and UI is good too. Are you simulating the Dynamic mesh by the way?