Combined Theoretical and Experimental Study of Phenomena Related to Limit CycleOscillations

摘要

A combined theoretical, computational, and experimental program has investigatedsituations where fluid motion and a flexible surface produce nonlinear interactions. The main cases of interest concern situations where an external flow field contains a significant disturbance, such as a vortex in subsonic flow or a shock wave in supersonic flow. This type of flow feature can produce pressure perturbations which may provoke movement in flexible panels on the surface, as well as unsteady viscous separation effects in the boundary layers, which are on all solid walls. The net result is a complex interaction between the external mainstream flow, the viscous boundary layers, and the flexible surface itself. These interactions produce complicated oscillations of the surface that are sometimes refereed to as limit cycle oscillations (LCO). This research addresses a number of fundamental problems of LCO, with the goal of establishing cause and effect relationships in relatively simple environments. Several computational and experimental studies of selected simplified interactions are described in the body of the report.