Flow visualization studies of free convection laminar-to-turbulent transition along a heated vertical plate in water induced by two-dimensional forced disturbances

Visual investigations have been made of threedimensional transition phenomena in the boundary layer along a vertical heated plate in water in free convection under controlled forced disturbances. Regions of intense shear as well as longitudinal vorticity have been noted in the course of the amplification of the Tollmien-Schlichting disturbance waves. In the outer region of the boundary layer longitudinal vortices were observed, occurring relatively early. In their amplification and decay process they rapidly destroy the regularity of the inflow to the boundary layer and indirectly affect the transition development nearer to the wall.