Laminar Boundary-Layer Breakdown
Final rept. 1 Oct 1990-30 Sep 1991
VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF ENGINEERING SCIENCE AND MECHANICS
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The objective of the work is to use dynamical system theory to determine the mechanisms that are responsible for the breakdown of laminar flows and to investigate the possibility of modifying the transition process to affect the subsequent well-developed turbulence structure. Experiments performed in low-disturbance wind-tunnels established two scenarios for the laminar-boundary- layer breakdown the fundamental- and subharmonic-modes of breakdown. The experimental observations of the subharmonic breakdown are very similar to our observations of the breakdown of regular motions in metallic and composite structural systems into chaotic motions. Therefore, we used dynamical system theory to conduct an analysis for the subharmonic breakdown in boundary layers similar to the one we successfully used to explain the breakdown in the response of the structural systems. The results can be used to modify the breakdown process and hence the resulting turbulent motion.