Numerical prediction of flow noise levels on towed sonar array

Flow noise originating in the turbulent boundary layer (TBL) often severely limits the performance of towed sonar array. Therefore, it is necessary to predict this noise for the design of an efficient towed array. This paper presents large eddy simulation methodology to establish the TBL properties and wall pressure fluctuations on a 12 m long towed array with length to diameter ratio of 1200 in the operating tow speed range of 2 to 5 knots in water. The computed flow noise levels are compared with experimental measurements available in the literature successfully. The effectiveness of scaling the flow noise spectra with the diameter and tow speed is discussed, and non-dimensional wall pressure spectra presented with respect to non-dimensional frequency. The overall sound pressure levels are also compared with experimental data that show good accuracy achieved by the proposed numerical methodology.