Estimate the required first cell height for CFD simulations based on target Y+. Uses turbulent flat plate correlation (Cf = 0.058 Re⁻⁰·²)—valid only for incompressible boundary layers over smooth flat plates. For separated flow, transition regions, rough surfaces, or compressible flows, consult empirical correlations or solve full Navier-Stokes equations.
Must be > 0
Must be > 0
Must be > 0
Must be > 0
Must be > 0 (1 for wall-resolved)
In Computational Fluid Dynamics (CFD), Y+ is a dimensionless distance from the wall. It is used to determine whether the boundary layer mesh is fine enough to resolve the viscous sublayer.
For simulations using wall functions, a Y+ between 30 and 300 is typically desired. For simulations that resolve the viscous sublayer directly (e.g., k-omega SST), a Y+ of approximately 1 is required.
Where u* is the friction velocity, y is the distance to the wall, and ν is the kinematic viscosity.
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