General method for determining the boundary layer thickness in nonequilibrium flows

While the computation of boundary-layer thickness is straightforward for canonical equilibrium flows, there are no established definitions general non-equilibrium flows. In this work, a method developed based on local reconstruction "inviscid" velocity profile $U_I[y]$ resulting from application Bernoulli equation in wall-normal direction. The $\delta_{99}$ then defined as location where $U/U_I = 0.99$, which consistent with its classical definition zero-pressure-gradient boundary layers (ZPGBLs). proposed local-reconstruction parameter free and can be deployed both internal external flows without resorting to an iterative procedure, numerical integration, or differentiation. superior performance over various existing methods demonstrated by applying laminar turbulent two airfoils. Numerical experiments reveal that more accurate robust than methods, it applicable wide range Reynolds numbers.