Y+ Number in ANSYS Meshing
 

Dear All,

I have been doing a supersonic flow analysis using ANSYS 15.07. My research involves a flow of Mach number 3.5 against a triangular obstacle and analyzing the various flow features like shock obstacle interaction, boundary layer separations, shock vortex interactions etc. in the downstream region of the flow domain. I am using unstructured meshes and my simulations are for transient cases. My computational boundaries are as follows, length is 120mm along the X direction and 30mm along the Y direction. The triangular obstacle has a height of 11mm and is kept in such a way that the tip of it faces the incoming flows as such. For the triangle there is 20mm in-front of it and and 89mm behind the obstacle as such. This is done because more flow features are observed for the downstream side. However the Y+ number given by ANSYS Meshing is quite astronomical. It is quite beyond any appreciable value. It is quite high as such. I just don't understand why the value is so high. What methodology does ANSYS use for deducing the Y+ number as such. Any updates on this will be gratefully acknowledged. Thanks......................

I have had several issues as well with determining the y+ value in ansys meshing. ultimately, I decided to write a user defined function which calculates the y+ value directly from the flow results. And then iterate on the mesh until you have the y+ values you want. The equations are pretty easy to implement.

Thanks for your input. You developed the UDF using C/C++ I presume, using the standard mathematical formulations in calculating the Y+ number...........and then implementing them using C/C++..............

Actually, I did it a longer way, and created a script in Matlab to calculate y+ given the first cell height and skin friction.

Im not sure if it would work, but you could try simply creating a new variable I Fluent rather than writing code in C.

Y+ number calculation in ANSYS
 

Dear Deenriqu,

Thanks for your further update.................. Actually I have some prior experience in developing UDF using C++ that's why I asked you. ANSYS is also developed using C++, correct me if I am wrong........................... The previous time I developed an UDF using C++, it worked well in ANSYS.

Regards,

Saikat