Boundary-layer thickness#Displacement thickness

The displacement thickness, a term of fluid mechanics ( boundary layer theory, ) is a measure of the displacement of the power lines to the outside due to the formation of the boundary layer. Considering the mass flow of the fluid, then corresponds to the displacement thickness of the shift to which you would have to drive at which forms the boundary layer to move, to get the same mass flow in the event of a disk without boundary layer.

Use the momentum thickness and displacement thickness can be determined as the ratio of the shape parameter H of a boundary layer:

The displacement thickness is defined as:

: Thickness of the boundary layer

: averaged velocity profile

: Inflow velocity of the infinite outer flow