Displacement Thickness

Definition

The Displacement Thickness ($\delta^*$) is the distance by which the external inviscid flow is displaced outwards due to the formation of the boundary layer. It represents the mass flow deficit.

Formula

$\delta^* = \int_0^\infty \left(1 - \frac{u(y)}{U_e}\right) dy$

Relationships

• Related: Boundary Layer, Momentum Thickness