Self-sustained Aeroacoustic Oscillations in Multiple Side-Branch Pipe Systems

Low frequency flow excited acoustic resonances have been observed in the pipe network of a compressor station. These pulsations have been identified as aeroacoustic oscillations sustained by the instability of the grazing flow along closed side branches of the pipe system. The investigation of this phenomenon is carried out on a scale model. Since the scale model shows an acoustic behavior similar to the compressor station it is used in order to characterize some of the design parameters that are influencing the aeroacoustic behavior of the pipe network. These parameters are the shape of the edges at the junction between the side branches and the main pipe, the depth of the side branches and the geometrical symmetry of the system. The resonance modes of the pipe network are predicted by means of a plane wave acoustic model. A model for the evaluation of the global maximum pulsation amplitude from the knowledge of a local maximum pulsation amplitude is then presented.