Learning Forum

[TRyder]

Hi, all
Before you read the rest of this, my CFD knowledge is almost rock bottom, so heads up.

Im trying to simulate 3D Jet impingement flow. My mesh is separated into three separate regions (one for the jet and initial impact, one for the remaining area on the impact plate and one for everywhere else). Im using SST and simulating a flow of Re = 10,000. To get my y+ under 5 I decided to use inflation layers. when I did my wall heat transfer coefficents have gone from a peak of ~300 to around ~980 which does not match with other data ive found. I have also noticed that when each zone had a different number of inflation layers, there was decreasing steps in the wall heat transfer coefficent.

I would like some advice on what might be causing this, I think the inflation layers are doing something to the wall heat transfer coefficents but im not sure if this is intended behavior or not.

Cheers, Toby

[SRP]

Hi,

The change in wall heat transfer coefficients (HTC) when using inflation layers in a CFD simulation can be influenced by boundary layer resolution (y+ value). A y+ value of less than 5 is commonly used for wall-resolved simulations, but it's essential to ensure that the y+ is properly resolved in your simulation.If your y+ values are not consistent across different mesh regions or layers, it could lead to variations in HTC. You should aim for a consistent y+ value across all mesh zones.

Hope this helps you.

Thank you.

[TRyder]

Thanks for the advice. I ended up solving it by calculating the wall heat transfer coefficent from the wall heat flux instead of the wall heat transfer coefficent straight from CFX. This managed to solve my problem.

Cheers, Toby