Generation of pre-set wavelength Gortler vortices

Abstract

The development of a??forceda?? wavelength G??rtler vortices in a laminar boundary layer flow generated over a concave test surface with 2.0 m radius of curvature has been investigated experimentally in the present study. Equally spaced finite length perturbation needles, instead of the conventional vertical wires, were used to pre-set the wavelengths of the vortices. Mean velocity measurements using a single hot-wire probe indicated that the new method is able to pre-set the wavelengths of G??rtler vortices for both free-stream velocities Ui?Y of 1.0 m/s and 3.0 m/s provided that the Reynolds Red, based on needle diameter and free-stream velocity, does not exceed a critical level. It was observed that the breakdown of vortices into turbulence occurred at a lower G??rtler number Gi?? for free-stream velocity Ui?Y of 3.0 m/s. The spanwise spacing between the needles was also varied to study the possible effects on the development of the G??rtler vortices.