Numerical Prediction of Aerodynamic Noise of Leakage Flow Using CFD/Caa Hybrid Method

The high speed flow leaked from cracks in gas pipelines can lead to severe explosion accidents. Therefore, detecting the location of leakage flow early and precisely is important to reduce the damage from leakage flow. The three-dimensional probe array using the acoustic intensity signals is one of the useful leak detection technologies. In this study, the CFD/CAA hybrid method is used to investigate the flow and acoustic characteristics of leakage flow. The features of leakage flow, including turbulence scales, roll-up phenomenon, strong shock waves, and Mach disk are predicted through the large eddy simulation (LES), and the far-field noise is calculated using the Ffowcs Williams-Hawkings (FW-H) acoustic analogy with permeable surfaces. The parametric study is performed in terms of the internal pressure condition in the pipe (10, 30, 50, 100 bar) and the size of leakage hole (5, 8, 10 mm) to analyze the flow and acoustics characteristics of the leakage flow. The strong Mack disk expands widely as the internal pressure and hole size increase while screech tone noise at specific frequency is observed as the internal pressure and hole size decrease. It turns out that overall sound pressure level (OASPL) of leakage flow increases about 15 dB when screech tone noise occurs.