Primitive Comparison of the Signal-to-Noise Ratios of Pressure and Velocity Planar Arrays.
Research and Development rept. 1 Jul-30 Sep 97
NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD SIGNATURES DIRECTORAT E
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The combined filtering efficiency of a pressure array and a velocity array, both flush mounted in a plane boundary, are derived and stated. The combined filtering efficiency is factorized into active and passive filtering efficiencies. The active filtering efficiency for the pressure array and for the velocity array are assumed to be identical except for a factor of the square of the characteristic impedance of the fluid that occupies the semi-infinite space above the boundary. This active filtering efficiency is related to the sensitivity of the transducers in the array and to the wave vector on the boundary to which the array is steered. The difference between the filtering efficiency in the pressure array and that in the velocity array lies in the respective passive filtering efficiencies. This difference is used to assess the signal-to-noise ratio pertaining to these two arrays the pressure array and the velocity array. Then an estimate is performed as to the advantage or the disadvantage that the pressure array may have compared with the velocity array. This estimate is made more explicit by considering the spectral density of the noise to be closely related to that of a turbulent boundary layer TBL.
- Fluid Mechanics