A Nonlinear Stability Approach to Boundary-Layer Transition Data Analysis.
Final rept. 1 Apr 77-14 Apr 78,
NEW YORK UNIV N Y DEPT OF APPLIED SCIENCE
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Findings and conclusions of a brief, seven month, effort on fundamental aspects of boundary-layer transition analysis and prediction are reported. Starting from the linear forced responsestability theories of Mack, the capabilities of the attendant maximum allowable linear disturbance amplitude criteria are examined in the context of selected transition experiments. Evidence of distinct nonlinear effects is found in the growth process of internal boundary-layer disturbances having small but finite amplitude heretofore assumed to fall within the realm of linear theory. The flow processes responsible for this behavior are identified, the formulation of an attendant nonlinear model differing from classical weakly nonlinear stability theory is set forth, and preliminary predictions, apparently explaining the complex multi-region stability diagram observed in recent experiments by Demetriades, are presented. An important role of nonlinear flow processes and models is suggested for transition data analysespredictions and an approach to elaboration of such models is outlined. Author
- Fluid Mechanics