y+ and wall distance

bye bye my blue · February 12, 2017, 07:03

Hi I'm simulating 2D aifoil with salome 7.8

I wanna wall distance. I made mesh with salome, and on FOAM got y+

my goal is 20<y+<30

on FOAM function (simplefoam -postprocess -func yPlus), I could got min :~ max : ~ average : ~

then, average : ~ is y+?? I don't know what is y+(min or max or average)

and at (http://www.pointwise.com/yplus/) there is wall distance (delta s), its mean is grid size in viscous layer??

Thanks

decah · February 12, 2017, 09:33

Hi there,

The y+ value will vary over your airfoil between the min and max values you got from the post-processing. If you want 20<y+<30 everywhere (is this the case?) then you need to adjust your grid so that y+_min and y+_max both fall within this range.

The calculator you shared a link to computes the grid size, delta s, along the wall that you need to achieve the specified y+. So plug in y+=20 and y+=30 on the left and it will tell you what grid size to use.

February 12, 2017, 07:03	y+ and wall distance	#1
bye bye my blue Member bye bye my blue Join Date: Sep 2016 Posts: 37 Rep Power: 8	Hi I'm simulating 2D aifoil with salome 7.8 I wanna wall distance. I made mesh with salome, and on FOAM got y+ my goal is 20<y+<30 on FOAM function (simplefoam -postprocess -func yPlus), I could got min :~ max : ~ average : ~ then, average : ~ is y+?? I don't know what is y+(min or max or average) and at (http://www.pointwise.com/yplus/) there is wall distance (delta s), its mean is grid size in viscous layer?? Thanks

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February 12, 2017, 09:33		#2
decah Member Declan Join Date: Oct 2016 Location: Ireland Posts: 40 Rep Power: 9	Hi there, The y+ value will vary over your airfoil between the min and max values you got from the post-processing. If you want 20<y+<30 everywhere (is this the case?) then you need to adjust your grid so that y+_min and y+_max both fall within this range. The calculator you shared a link to computes the grid size, delta s, along the wall that you need to achieve the specified y+. So plug in y+=20 and y+=30 on the left and it will tell you what grid size to use.