Effect of Intensity of the Disturbance on the Downstream Development of the Laminar Spot

Abstract

In the final stage of laminar to turbulent transition, it was known that the regions called ‘turbulent spot' appear. When these spots develop downstream and the boundary layer fill with them, the transition process is finished. Previous studies have shown that development of spot was arranged by the energy of jet unrelated these shapes. The purpose of this study was to clarify growth and development proses of the spot using some shapes jet with same energy. From results obtained, the spot created by sharp jet grew faster than that created by flat-shape jet. In the spot created by flat jet, hair-pin type vortex induced secondarily was weak and wider than first one. The wide hair-pin type vortex could not create a strong low-speed shear layer between its legs. Consequently, growth of the spot created by flat-shape jet became slow.