Integral characteristics of the boundary layer in relaxation zone after a local closed separation

Abstract

The results of the experimental study of the integral characteristics (friction and heat transfer coefficients, profiles of velocity and temperature, characteristic thicknesses and shape parameters) are presented for the relaxating flow downstream of a separation of various types in case of low free stream turbulence Tue  0.2 % and velocities of an external flow Ue  5 - 10 m/s. The type of a separation (laminar, transitional or turbulent) is adjusted by the shape of an inlet edge of the plate and the length of an intercepter, installed in the test section of the wind tunnel. The measurements confirm extremely slow recovery to a ”classical” turbulent boundary layer after various types of a separation. They also demonstrate the dissimilarity of an internal structure and different rates of recovery in hydrodynamic and thermal boundary layers in relaxation zone both in an inner region and at an outer part of ones.