Generation, Development and Distortion of Longitudinal Vortices in Boundary Layers Along Concave and Flat Plates

Abstract

A linear stability analysis has revealed the non-parallelism of flows as one of the factors causing the generation of longitudinal vortices in boundary layers. This has been experimentally verified through water tank tests for a concave plate and wind tunnel tests for a flat plate. Longitudinal vortices generated in the boundary layer on concave plates, i.e., Gortler vortices, as they develop, generate horseshoe type vortices as a secondary instability. Nonlinear interaction between these vortices promotes collapse of the vortices or the transition to turbulence. Even after the transition, organized three-dimensional structures are recongnized in the boundary layer.