Integral Thicknesses 1 Definitions The details of the velocity profile u(y) at any a location are rarely significant in engineering applications. The most significant quantities are integral thicknesses which describe the mass Aux, momentum flux, and kinetic energy flux in the shear layer displacement thickness Pete dy momentum thickness Pe 0·= kinetic energy thickne 2 Integral Thickness Interpretation These thicknesses appear when comparing the mass, momentum, and kinetic energy fows in a shear layer and a corresponding potential flow 2.1 Mass flow comparison Figure 1 shows the mass fux passing between the vertical extent y=0... Je for inviscid and viscous fows with the same velocity. ye ye Figure 1: Comparison of inviscid and viscous mass flows dy= rir pewee pu dy u dy I- peu The viscous mass fow is decreased by an amount equal to the mass defect pete 8