边界层计算中的y+如何设置，具体计算方法

twq728

用边界层计算边界层厚度时，发现有一个空y+，不知道它具体表达什么意义，是根据什么得出的！初学者不懂，还望各位大侠帮忙

twq728

liuoseulb

FLUENT User's Guide
<Near-Wall Mesh Guidelines for Wall Functions>
1. For standard or non-equilibrium wall functions, each wall-adjacent cell's centroid
should be located within the log-law layer, 30 < y+ < 300. A y+ value close to the
lower bound (y+ =30) is most desirable.
 2. Although FLUENT employs the linear (laminar) law when y*< 11.225, using an
excessively ne mesh near the walls should be avoided, because the wall functions
cease to be valid in the viscous sublayer.
 3. As much as possible, the mesh should be made either coarse or ne enough to
prevent the wall-adjacent cells from being placed in the buer layer (y+ = 5~30).
 4. The upper bound of the log-layer depends on, among others, pressure gradients
and Reynolds number. As the Reynolds number increases, the upper bound tends
to also increase. y+ values that are too large are not desirable, because the wake
component becomes substantially large above the log-layer.

[ 本帖最后由 liuoseulb 于 2011-10-10 22:06 编辑 ]

乘风破浪cf

y+简单来说，是在划分网格时候使用的，它决定边界层第一层的厚度。一般情况下取值在（30，300）之间。通过fluent计算后，可以通过Display>Contours…> Contours of /Turbulence  /Wall Yplus
进行查看，如果显示y+ 的值大于该范围，应该加密该区域网格，重新计算，再查看y+ ，如果仍不在其范围，继续加密网格，如果小于该范围就要粗化。 壁面网格加密可采用自适应网格。
加密时采用Adapt>Y+/Y*…，Options选项，只选Refine ；Type选Y+；点击Mark，再点击Adapt；及完成网格加密
粗划时， 采用Adapt>Y+/Y*…，Options选项，只选Refine ；Type选Y+；点击Mark，再点击Adapt；及完成网格粗划。
希望对你有帮助。具体怎样计算y+时，比较复杂，你可以找下资料学习下，我也正在学习中。