Cavity Pressure Oscillations: The Generating Mechanism Visualized

Kurzfassung

Renewed interest in understanding and solving the problem of intense pressure oscillations in shallow rectangular cavities subject to an external transonic flow has led to a number of recent publications proposing physical generating mechanisms and theoretical models to predict oscillation frequencies (1,2) and mostly empirical models to predict levels (3,4). A good up-to-date survey has appeared in reference (5). For a typical such cavity of, say, L &#61 4m length, D &#61 0.75m depth and W &#61 0.6m width, under M &#61 1.2 flow, pressure levels near the cavity trailing edge are to be expected which would by far exceed values of 160dB (re2x10**N/m*) at frequencies low as f*&#6130Hz, f*&#6170Hz and f*&#61110Hz, approximately, for the first three modes. If such a cavity were imbedded in an aircraft's exterior surface, the high oscillation intensities at these low frequencies could lead to structural fatigue of airplane components and could adversely affect nearby electronic equipment.