Aspect ratio near boundary for moderate Re

quarkz

I am simulating airfoil flows at moderate Re of 10,000. I am using structured grids.

Using the flat plate estimation, the boundary layer is around 5/sqrt(10,000) = 0.05. Assuming 30 cells, the cell thickness near the boundary should be around 0.05/30 ~ 1.6e-3.

I wonder what is the acceptable range of aspect ratio near the boundary? If my 1st cell distance is 1.e-3, is that acceptable?