Aeroacoustic analysis of flow induced resonance in a gas pipeline

Flow induced noise and vibration in the pipework of gas production platforms can lead to fatigue failures of attached small-bore pipes, and this can constrain the operating conditions of the platform. Typically such problems comprise a source of turbulence in the flow, an aeroacoustic feedback mechanism due to acoustic resonances inside the pipework, and mechanical resonances which amplify the resulting vibration. The problem described here occurred in the gas metering system of the platform, with the source located in the header which comprised a bifurcation into two metering lines and a number of sharp bends. Because of the cost of rectifying the problem an in-depth study was carried out to analyse the flow and induct acoustic conditions. The predictions will support recommendations for an efficient redesign of the entire system to control the problem at source. Various levels of CFD modelling (RANS and URANS) were carried out using the Openfoam code to predict the exact location and mechanism of the vortex shedding. The acoustic response of the complex ductwork was then modelled using the ACTRAN code to understand the feedback mechanism which led to resonance and high levels of response.