Time-Dependent Modeling of Underwater Explosions by Convolving Similitude Source with Bandlimited Impulse from the CASS/GRAB Model
NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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The research documented in this report was conducted to develop a time-dependent pressure computational model for an explosive source in an underwater acoustic waveguide. This objective was accomplished by convolving a time-dependent similitude source with the farfield impulse response from the Comprehensive Acoustic System SimulationGaussian Ray Acoustic Bundle CASSGRAB model. The impulse response was found by performing an inverse fast Fourier transform of the frequency-dependent, bandlimited transfer function Green s function from CASSGRAB. The bandlimited transfer function is determined using the CASSGRAB amplitudes and phases over a range of frequencies. The result of this convolution is a time-dependent pressure field that satisfies the time-dependent hyperbolic wave equation with boundary conditions, which, in turn, produces a time series from the explosive source. In addition to describing the conduct of this investigation, this report presents the algorithm developed for the computational model and provides a comparison of measured and modeled data.