Calculations of the Flow Noise from a Turbulent Boundary Layer for Acoustic Vector Hydrophones in the Flank Array

Abstract

The flow noise for the acoustic vector hydrophone in the flank array is studied in this paper. The hydrophones are usually mounted above the baffle and are protected by a dome. This paper simplifies the flank array to be an infinite dome placed above an infinite baffle model, and the acoustic vector hydrophone is located in the fluid layer between the dome and the baffle. The spectral reflection coefficient of the multilayer baffle is obtained by the transfer matrix and matched boundary conditions. The cross-spectral density matrix is derived by the wavenumber–frequency spectrum analysis method. In addition, the spectral transfer functions are verified by the finite element method. Numerical results are presented to illustrate the influence of the free-stream velocity, the dome parameters, the location of the acoustic vector hydrophone and the baffle on the auto-power spectra of each hydrophone. Besides, the cross-power spectra of each hydrophone and the spatial correlation are discussed in this paper. The particle velocity channels are more sensitive than the pressure channel to the flow noise below 4000 Hz if the hydrophone is near the dome. The cross-power spectra between the pressure and particle velocity are lower than the particle velocity power spectra in the whole frequency band, and that are lower than the pressure power spectra in the higher frequency. The spatial correlation radius of the pressure and the particle velocity of all directions is small.