Y plus

abdul · April 18, 2009, 16:44

I am using different discretization schemes in Fluent to predict accurate results, discretisation schemes such as PRESTO for Pressure, second order upwind for Continuity etc etc

different discretisation schemes for the same 3d model, however when i refine the Yplus values to a certain limit and reducing it so there are 0 cells to refine, the amount of cells that are being refined vary accordingly to the different schemes, does anyone know why?

surely they should be the same amount of cells refined?

vishyaroon · April 20, 2009, 08:45

Your y+ values are based on the wall shear stresses. These are going to be as different as the near wall stresses predicted by the schemes you use. So in short you may not end up with the same y+ using different schemes. This is why you observe that you may have to refine your grids over and over again.

Another thing I'd point out is even after you refine the grid, your solution is going to be different from what you had using the coarser grid. Hence you'll again have different y+ values.

April 18, 2009, 16:44	Y plus	#1
abdul New Member abdul Join Date: Mar 2009 Posts: 8 Rep Power: 17	I am using different discretization schemes in Fluent to predict accurate results, discretisation schemes such as PRESTO for Pressure, second order upwind for Continuity etc etc different discretisation schemes for the same 3d model, however when i refine the Yplus values to a certain limit and reducing it so there are 0 cells to refine, the amount of cells that are being refined vary accordingly to the different schemes, does anyone know why? surely they should be the same amount of cells refined?

April 20, 2009, 08:45		#2
vishyaroon Senior Member Aroon Join Date: Apr 2009 Location: Racine WI Posts: 148 Rep Power: 17	Your y+ values are based on the wall shear stresses. These are going to be as different as the near wall stresses predicted by the schemes you use. So in short you may not end up with the same y+ using different schemes. This is why you observe that you may have to refine your grids over and over again. Another thing I'd point out is even after you refine the grid, your solution is going to be different from what you had using the coarser grid. Hence you'll again have different y+ values.