Numerical simulation regarding flow-induced noise in variable cross-section pipelines based on large eddy simulations and Ffowcs Williams–Hawkings methods

Large eddy simulations and Ffowcs Williams–Hawkings acoustic analogy methods have been adopted to simulate the flow-induced noise for variable cross-section pipelines under variable flow velocity conditions in this paper, and the main influencing factors of flow-induced noise are analyzed numerically, including the flow velocity and variable diameter angle. Results manifested that the flow field distribution, sound source characteristics, and frequency spectrum characteristics of the sound pressure level (SPL) at different flow velocities follow similar trends. The average acoustic source intensity increases gradually with the increase in flow velocity. The maximum of the acoustic source intensity is located near the outlet of the variable diameter angle due to the vortex effect. The flow-induced noise in variable cross-section pipelines is mainly low-frequency noise, and its energy is mainly concentrated below 200 Hz according to the frequency spectrum characteristics. Additionally, the SPL increases with the increase in flow velocity. Compared with v = 1 m/s, the SPL at v = 2 m/s and v = 3 m/s increases by 9.4% and 22.1%, respectively. In addition, there is an approximate linearly increasing relationship between the SPL and the variable diameter angle. The minimum of the SPL appears at φ = 15.2°, and the maximum appears at φ = 25.7° at different flow velocities, which is up to 70.18 dB. Briefly, the flow-induced noise characteristics, including the average acoustic source intensity, the SPL, and the frequency spectra, are revealed in this paper. This provides a theoretical basis for the optimization of variable cross-section piping systems and the investigation of flow-induced noise control techniques.