Experiments on streamwise vortices in curved wall jet flow

Hot-wire anemometry and smoke visualizations are used to study the jet on a concave wall. The measurements were performed in the region 91<Go<198, where Go is the Görtler number. It is found that streamwise vortices are amplified on the concave wall. The growth of vortices is dependent on the initial amplitude, i.e. the highest initial amplitude gives the maximum strength of vortices. The amplification occurs in the laminar region while the time-averaged strength of vortices decreases further downstream in the transition region. No merging or splitting of vortex pairs was found. Regular oscillations of the time signal occur at higher Görtler numbers before breakdown. Smoke visualization shows that the horseshoe mode appears with a streamwise wave length of the same order as the triggered spanwise wave length. The streamwise velocity fluctuations indicating the secondary instability were found to coincide better with the total shear distribution rather than streamwise velocity ...