Numerical analysis of vibroacoustic beamforming gains for acoustic source detection inside a pipe conveying turbulent flow

This study concerns a monitoring technique based on vibration measurements for identifying the presence of an acoustic source in a fluid-filled pipe conveying turbulent flow. In such situation, the source-induced vibrations can be smeared with the flow-induced vibrations, which hinders the source detection. To increase the signal-to-noise ratio (SNR), beamforming techniques can be applied to the vibrations measured by an array of accelerometers mounted on the pipe. However, the current problem is more complex and challenging than most typical beamforming applications due to strong fluid–structure coupling and to the presence of resonant modes and internal flow excitations. Numerical vibroacoustic methods are presented to predict the vibratory response of a pipe excited by a monopole source and/or a turbulent boundary layer (TBL). The cross-spectral matrices of the computed radial accelerations induced by the monopole source to be detected and by the TBL are used for assessing the performance of two vibroacoustic beamforming techniques. The array gains using both, the conventional and the MaxSNR beamforming approaches are estimated. Results indicate superior performance of the MaxSNR, which leads to significantly higher array gain.