Y+ (y-plus) Calculator - First Cell Wall Distance for CFD

Your details

Choose whether to find the wall spacing from a desired y+ or to evaluate an existing spacing.
Characteristic or far-field flow speed used to compute the Reynolds number.
m/s
Characteristic body length (flat plate length, chord, hydraulic diameter, etc.).
m
Target dimensionless wall distance. Use ~1 for SST/LES, 30-300 for wall functions.
First cell heightWall-resolved (y+ <= 1)
3.254e-5 m

Required distance from wall to first mesh node (or cell centre for cell-centred solvers)

Computed y+1
Reynolds number684,740.078
Friction velocity (u_tau)0.4488 m/s
Wall shear stress (tau_w)0.2468 Pa
Skin friction Cf0.004029
Flow regimeTurbulent (low-Re)
1
Wall-resolved<1Viscous sublayer1-5Buffer layer5-30Log-law / Wall functions30+

y+ = 1.00 - well-resolved wall.

  • y+ = 1.00 sits in the viscous sublayer. This is suitable for low-Reynolds turbulence models and most RANS models without wall functions.
  • Reynolds number is 6.85e+5, placing the flow in the turbulent regime where the Schlichting power-law correlation applies.

Next stepUse the first cell height shown as the wall-normal spacing for your first prism or inflation layer. Stack subsequent layers with a growth ratio of 1.1-1.3.

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