The asymptotic solution for broadband pulse in hydroacoustic waveguide shallow sea with an losses bottom
UDC
534.231Abstract
The calculation of the response of the waveguide on a pulse signal is one of the challenges of acoustics shallow sea. In the case of a waveguide with an losses bottom the character of dispersion of the group velocity of normal modes becomes more complicated compared to the waveguide without lossless bottom. In the article the impulse responses of individual modes in a hydroacoustic Pekeris waveguide with an losses bottom are calculated by the method of stationary phase. The impulse response of the normal mode are represented as the inverse Fourier transform from the separate mode acoustic field calculated in a broadband frequencies. Dispersion relation is solved numerically by the method of Newton-Raphson. The inverse Fourier integral is calculated using the method of stationary phase. As a result, temporal implementation of a pulsed field is represented as a sum of three waves - ground wave, water wave and Airy wave. When calculating the Airy wave corresponding to the frequency dependence extremum of the group velocity of mode uses the decomposition to the fourth term of the series. The conditions for the applicability of the method of stationary phase for the waveguide with an absorbing bottom are specified. It is shown that the use of the method of stationary phase to compute an impulse response of the waveguide requires the application of additional condition of the waves coupling to getting unbroken and smooth implementation of the signal. It is shown that the conditions for the application of the method of stationary phase is improved by increasing the distance between the source and the receiver.
Keywords:
hydroacoustic waveguide, normal mode, wavenumber, impulse responseReferences
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Copyright (c) 2015 Lastovenko O.R., Lisyutin V.A., Malenko Z.V., Yaroshenko A.A.
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