Y+ Calculator

Formula

The formula to calculate Y+ is:

\[ Y+ = \frac{y \cdot u}{v} \]

Where:

\(Y+\) is the local Reynolds number
\(y\) is the absolute distance from the wall (meters)
\(u\) is the friction velocity (m/s)
\(v\) is the kinematic viscosity (m²/s)

What is Y+?

Y+ is a term used in computational fluid dynamics (CFD) to describe a "local Reynolds number" of flow near a wall. Y+ is dimensionless and unitless. It is crucial in determining the near-wall treatment in turbulence models and helps in assessing whether the mesh resolution is sufficient to capture the boundary layer flow characteristics accurately.

Example Calculation

Let's assume the following values:

Absolute Distance from the Wall (y) = 0.005 meters
Friction Velocity (u) = 0.1 m/s
Kinematic Viscosity (v) = 1.5e-5 m²/s

Using the formula to calculate Y+:

\[ Y+ = \frac{y \cdot u}{v} = \frac{0.005 \cdot 0.1}{1.5e-5} = 33.33 \]

The Y+ is 33.33.