An envelope method for detection of turbulence intermittency in a transitional boundary layer

Abstract

Extensive hot-wire anemometer measurements have been carried out in a flat plate boundary layer undergoing transition from laminar to fully turbulent flow. The main aim of the present work is to develop a convenient and objective method which can be applied to streamwise velocity fluctuations to obtain distributions of the turbulence intermittency factor across the boundary layer in the transition region. For this purpose, based on the M-TERA (Modified Turbulent Energy Recognition Algorithm) method, an envelope method, called EM-TERA, employing two detection criteria for detection of turbulence intermittency, is proposed. The results indicate that this method can detect the turbulence intermittency conveniently and reliably with its two respective threshold coefficients kept constant (C1 = 0.5 and C2 = 0.01) in the entire transitional region of a boundary layer, except for the very near-wall region.