An Experimental Study of Boundary-Layer Transition

Abstract : The transition from laminar to turbulent flow on a smooth flat plate in a zero pressure gradient was studied in a wind tunnel by using conventional surface-tube and hot-wire techniques. In the 0.10 to 0.5% range of free-stream turbulence, the laminar oscillations predicted by the Tollmien-Schlichting theory of laminar-layer stability appeared to play an important role in transition. In the process of transition which was similar to the development of a turbulent wake from a vortex street, the amplified frequency fed the rest of the spectrum. A study of the effect of free-stream turbulence on transition, in terms of the energy concentrated at the amplified frequency, revealed that the free-stream turbulence hastened the feeding of energy from the amplified frequency to the rest of the spectrum. Laminar oscillations appeared to play no part in transition at much higher levels of free-stream turbulence. A suggested possible control for transition theory proposed by Taylor.