Visualization of Developing Processes of Longitudinal Vortices Produced in Turbulent Wall Jets along a Strongly Concave Surface

Abstract

Developing processes of longitudinal vortices produced in turbulent wall jets along a concave surface are studied by flow visualization with smoke-wire method and moving laser-sheet technique. It is found that the formation of the vortices is mainly due to the spanwise secondary-flow-motion in the wall region, while they grow normal to the surface in the downstream reaching to the middle of the jet region. The vortices in the downstream are strongly affected by the intermittent turbulent-structure in the jet region so that they behave unsteadily in space and time .