# Shape Factor (Boundary-layer thickness)

## Description

A shape factor is used in boundary layer flow to determine the nature of the flow.

The higher the value of H, the stronger the adverse pressure gradient. A high adverse pressure gradient can greatly reduce the Reynolds number at which transition into turbulence may occur.

Conventionally, H = 2.59 (Blasius boundary layer) is typical of laminar flows, while H = 1.3 – 1.4 is typical of turbulent flows.

## Variables

H | shape factor (dimensionless) |

δ* | displacement thickness (m) |

θ | momentum thickness (m) |