Numerical modeling of laminar-turbulent transition in a boundary layer at a high freestream turbulence level

Abstract

Disturbances generated by external turbulence in the boundary layer on a flat plate set suddenly in motion are determined by numerically solving the Navier-Stokes equations. The results of direct numerical simulation of isotropic homogenous turbulence are taken as initial conditions. The solution obtained models laminar-turbulent transition in the flat-plate boundary layer at a high freestream turbulence level, time measured from the onset of the motion serving as the longitudinal coordinate. The solution makes it possible to estimate the effect of different factors, such as flow unsteadiness and nonlinearity and the characteristics of the freestream velocity fluctuation spectrum, on laminar-turbulent transition in the boundary layer.Here, U 0 (z, t) is the mean flow velocity which is equal to zero before the plate appears and corresponds to the laminar flow velocity profile in the channel after it appears, while 2L x and 2D are the longitudinal