Optimized shapes of oscillating resonators for generating high-amplitude pressure waves

Several studies have proved that the geometry of an oscillating acoustic resonator strongly influences its resonance frequencies and the nonlinear standing pressure waveform generated within the cavity. The research presented herein uses a quasi-one-dimensional numerical model to solve the acoustic field and is validated by comparing with experimental results. A quasi-Newton type numerical scheme is used to optimize the axisymmetric cavity contour by maximizing the pressure compression ratio, defined as the ratio of maximum to minimum gas pressure at one end of the oscillating resonator. Cone, horn-cone, and cosine resonator contours are each optimized for a fixed amplitude of the periodic external force oscillating the cavity. Different optimized shapes are found when starting with different initial guesses, indicating multiple local extrema. The maximum pressure compression ratio value of 48 is found in an optimized horn-cone shape. This represents a 241 % increase in the compression ratio over any previously published results. (C) 2004 Acoustical Society of America.