Abnormal Inflation Layer Compression and Stair Stepping while generating mesh over Wing

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  • Last Post 20 August 2019
AnkithJohn posted this 19 August 2019

My project deals with the influence of ground effect aerodynamics of a wing. In order to do this, I am first carrying out a verification and validation study of the same wing in unbounded flow, to determine which turbulence model would be the most suitable to use.
To do this, I intend to create a mesh that resolves the boundary layer to a very good resolution where in the Y+ value should be on average around 0.5.  The mesh consists of two added refinement regions using the body of influence method. The outer body with an element size of 0.08 meters and the inner body with a refinement of 0.04 meters. The idea is that these extra levels of refinement will help in slowing down the growth of the mesh in proximity of the wing to facilitate a better capture of flow properties. 

Issues I'm facing:    As you can see in Image2.JPG, when I add the inflation layers, towards the trailing edge of the wing, I start to see abnormal stair-stepping of the inflation layers and layer compressions (the software however gives no warning/message of this like it usually does). I have tried adjusting the gap factor, maximum height over base and other parameters but I see no improvement.  Is there any advice that you could provide to help rectify this issue. 

Thank you so much. 

Mesh Details:

Inflation: 38 layers , first cell height= 8.9 e-6 metres,  growth rate= 1.2, gap factor= 1, maximum height over base= 0.7, maximum angle= 180 degrees  (applied on the faces of the Flying V)

Surface Mesh: Created using face sizing and edge sizing where the number of divisions along the edges were varied depending on if the edge is along the span-wise or chord-wise direction. A Bias factor of 8.0 was applied only along the edges in the chord wise direction.   

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peteroznewman posted this 19 August 2019

ANSYS staff can't open attachments. Please Insert Image directly in your post.

rwoolhou posted this 20 August 2019

Stair stepping is a way for the tools to collapse the inflation layer in a controlled manner if it won't fit into the gap or conflicts with your other settings. Rather than mess with all the inflation settings have a look why it's doing that. 

Also, as Peter pointed out, I am not allowed to open the image. 

AnkithJohn posted this 20 August 2019

Thanks for reaching out Peter. I've reattached the image to the post. Is it possible to view the image now?

AnkithJohn posted this 20 August 2019

Thank your or your message. I do not think there are gaps present, as this is over the surface of a pretty simple wing geometry. I believe the inflation layer start collapsing at a very localized region of the wing, however, when looking at multiple cross section slices I see that the inflation layers have actually  accurately been produced over the wing. 

I have reattached the image to my post. Let me know if you cannot see it yet. 

 

AnkithJohn posted this 20 August 2019

rwoolhou posted this 20 August 2019

Can you check you've picked all of the faces for inflation? 

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