[InfernoxCJC]

Hello everyone,
I'm still pretty new to CFD so forgive me if I am missing something obvious on just being generally stupid.

I am working on a simulation of a reference vehicle model for use in a Wind Tunnel in STAR. The model utilises legs as opposed to wheels and the region has had to be refined to a pretty decent resolution just to be rendered correctly. The issue I am having is with the Wall Y+ on these legs, primarily where the leg meets the floor of the Wind Tunnel.

Using STAR's 'Near Wall Thickness' Prism Layer model, I have successfully resolved the main body of the model to a Y+ < 1 for use of the Low Y+ Wall Treatment, but these leg-floor boundaries are stuck in that undesirable 1 < Y+ < 30 region and I'm not sure how to proceed. Using ever smaller Near Wall cell sizes doesn't resolve the issue even as low as 1E-6.

Are there any other methods I can use to achieve a lower Y+ value? or at least boost these isolated regions to Y+ > 30? Perhaps by locally removing the Prism Layers entirely?

Thanks for your help!

[AndreP]

Originally Posted by InfernoxCJC

Hello everyone,
I'm still pretty new to CFD so forgive me if I am missing something obvious on just being generally stupid.

I am working on a simulation of a reference vehicle model for use in a Wind Tunnel in STAR. The model utilises legs as opposed to wheels and the region has had to be refined to a pretty decent resolution just to be rendered correctly. The issue I am having is with the Wall Y+ on these legs, primarily where the leg meets the floor of the Wind Tunnel.

Using STAR's 'Near Wall Thickness' Prism Layer model, I have successfully resolved the main body of the model to a Y+ < 1 for use of the Low Y+ Wall Treatment, but these leg-floor boundaries are stuck in that undesirable 1 < Y+ < 30 region and I'm not sure how to proceed. Using ever smaller Near Wall cell sizes doesn't resolve the issue even as low as 1E-6.

Are there any other methods I can use to achieve a lower Y+ value? or at least boost these isolated regions to Y+ > 30? Perhaps by locally removing the Prism Layers entirely?

Thanks for your help!

If you remove the prism layers locally your Y+ will be too large. It depends how you're splitting your part. But if you have a separated part or surface for the feet, you can assign different sizes of the prism layers, and in that case, you can have a larger thickness or fewer prism layers locally! I think that fewer prism layers on the feet will do the trick for you!

[InfernoxCJC]

Thanks Andre,
Before actually reading your post I had the idea to split the geometry into multiple Boundaries and utilised different thicknesses for each as you suggested, this (largely) resolved the issue!