Measurement in laminar and transitional boundary-layer flows on concave surface

Abstract

Measurements of streamwise mean and fluctuating velocities in laminar and transitional boundary-layer flows on a concave surface of 2.0 m radius of curvature have been performed using hot-wire anemometry technique. A new turbulent intermittency detector method was used to calculate the intermittency factor. In addition to the spanwise distributions of mean velocity, the profiles of mean, fluctuating velocities and intermittency across the boundary layer at two different spanwise positions; namely, the upwash and downwash, are also presented. The experimental results show that the normal and spanwise distributions of mean velocity, normal turbulence intensity u′rms/U0 profiles experience different streamwise evolutions in the laminar and transition regions. Significant velocity profile distortion, saturated growth of Goertler vortices, and the existence of two peaks in u′rms/U0 profiles are the main features of the boundary-layer low at the onset of transition. The intermittency profiles in the early stages of transition t the two spanwise positions have some similar characteristics and are not consistent vith each other on some other aspects. Comparisons of the y profiles at the two spanwise positions confirm that the transition first starts at the low-speed regions. © 1995 Elsevier Science Inc.