Experimental analysis of the whistling of an industrial riser

The acoustic field induced by a flow in a corrugated pipe has been studied for a long time. There has been renewed interest in the development of offshore gas exploitation using long riser lengths for gas transport. On such installations, the phenomenon can lead to a failure of the equipment adjacent to the risers. In this context, a Flow-Induced Pulsations (FLIP) test was performed in a 6" internal diameter and 18-meter-long flexible pipe. This riser was equipped with upstream and downstream measuring couplers on which were fixed hot wire velocity sensors, pressure sensors and microphones. A series of tests was conducted for various internal pressures and flow rates. We present a time-frequency analysis of the signals resulting from these tests as well as a correlation study between the various sensors. We observed that the signals measured in the whistling condition showed significant temporal and frequency fluctuations. We were able to show that the frequency fluctuations were related to the geometry of the riser. In addition, these analyses made it possible to show that the whistling exists at transverse acoustic frequencies of the riser while propagating at the convective velocity of the flow.