The Unsteady Cavity in Internal Flows

Citation

Kim, Jong Hyun (1971) The Unsteady Cavity in Internal Flows. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Q343-FG73. https://resolver.caltech.edu/CaltechTHESIS:06112018-095816439

Abstract

The problems of the two-dimensional unsteady cavity in internal flow are treated and linear theories are developed. In Part I, the two- dimensional supercavitating flow past a flat plate heaving and pitching with small amplitudes in a choked tunnel is investigated and a linearized solution is obtained using the acceleration potential. The flat plate is inclined at a small angle of attack to the oncoming flow and the cavity pressure is assumed to be constant. Force and moment coefficients are calculated for the case of the foil placed in the middle of the walls as functions of reduced frequency and the ratio of tunnel height to chord length. The pressure disturbances caused by the unsteady motion of the foil do not die out far upstream; these also depend on the chord-tunnel height ratio and reduced frequency.

Another type of cavity problem in an internal flow is studied in Part II. Here, the finite cavity flow over a wedge held stationary in the middle of a tunnel is investigated. A salient feature of the problem is that the mass oscillation is allowed. Also the pressure on the cavity is allowed to vary in a prescribed manner. The problem is linearized using the complex perturbation velocity and the formal solution is obtained. The choked case in the presence of the overall mass fluctuation is obtained as a limiting case. Throughout the analysis, it is assumed that the change of the cavity length with time is small.

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