[futureamour]

Hello,

I am simulating the free surface turbulent flow of a water jet exiting a pelton wheel and I have some questions, that I would be grateful if someone can clarify to me.
1)the SST model I am using needs to have a y+ value for the adjacent to the wall cell of ~1.But also in the manual it says that Enhanced Wall Treatment that is the default for SST is y+ independent,and that the number of cells resolving the boundary layer is much more important.What is the story there?

2)If I try to make the y+ ~1,is there a difference between designing a very fine mesh that achieves this value(through the y+ calculator) and making a rather coarse mesh (with y+ ~50) and then perform 5-6 y+ adaptions (setting min 1, max 5) to refine it by decreasing the y+ value?Is there any limit in the # of adaptions you can safely perform?

3)There is little information about turbulence damping.In the manual it says that it is highly recommended for vof simulation,yet in the tutorial simulation of vof in the manual they do not use it.When i used it, I got rather weird results.Any thoughts?

4)Is there any post processing contour where I can see if I have accurately solved the b layer and if I have sufficient # of cells to capture it?

Any thoughts-suggestions, highly appreciated!!
Sorry for the lengthy post

[macfly]

Originally Posted by futureamour

I am simulating the free surface turbulent flow of a water jet exiting a pelton wheel and I have some questions, that I would be grateful if someone can clarify to me.
1)the SST model I am using needs to have a y+ value for the adjacent to the wall cell of ~1.

If it's a free surface flow, a water jet in the air, why do you consider walls?

Originally Posted by futureamour

2)If I try to make the y+ ~1,is there a difference between designing a very fine mesh that achieves this value(through the y+ calculator) and making a rather coarse mesh (with y+ ~50) and then perform 5-6 y+ adaptions (setting min 1, max 5) to refine it by decreasing the y+ value?Is there any limit in the # of adaptions you can safely perform?

Mesh adaption is very costly because a hexahedron is cut into 8 hexahedrons, and chances are you need to refine only along 1 coordinate (perpendicular to flow direction). If you refine manually, you will cut 1 hexahedron into 2 hexahedrons, not 8.

[futureamour]

Thanx for the reply!

Regarding the first question,the water jet is leaving the nozzle,so I have to consider also the nozzle (outer wall) and the regulating spear (inner wall).Sorry for not being clear enough about it.