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#1 |
Senior Member
Brett
Join Date: May 2013
Posts: 212
Rep Power: 14 ![]() |
Hi all,
This has probably been asked before. I understand what the y+ value is, but what I'm hoping to get some clarity on is how does turbulence model selection affect the required y+ value of the first cell? Building on that, what are the different types of wall functions and when are they applied? to my knowledge wall functions are applied to model, not resolve, the physics below the first cell. So if you're first cell is in the buffer layer then a wall function could model the flow closer to the wall even though you don't have cells close enough to resolve that. Any thoughts most welcome. B |
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#2 | ||
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,728
Rep Power: 66 ![]() ![]() ![]() |
Quote:
Quote:
Wall functions never resolve anything, they're merely boundary conditions. The physics are dictated by the physics equations (the navier-stokes equations and the turbulence model being used). Whether or not the physics are resolved depends on those equations and whether the grid provides the resolution needed to resolve them. Wall functions always model what happens underneath the first cell; because, the physics certainly can't, there's no grid there! It's inaccurate to say the wall function can model the flow near the wall below the first cell, it MUST or you will have the wrong solution. You can't really talk about a wall function without first declaring what turbulence transport equation you have that it is meant to provide boundary conditions for. |
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Tags |
boundary layer, turbulence, wall function, y plus, y plus ranges |
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