Transient flow and noise characteristics of accelerated flow past a hydrofoil with special emphasis on vortex-turbulence-noise interaction

Abstract

The transient process is widely existed in hydraulic machinery and engineering application, which is closely related to the flow and noise characteristics. In the present work, the large eddy simulation turbulence model is employed to simulate the transient flow of accelerated flow past a NACA0015 hydrofoil. The Reynolds number is 8000, the attack angle is 30°, the inlet velocity accelerates from zero to 0.1 m/s with acceleration of 0.1 m/s2, the acceleration time is 1s. Then the broadband noise source model is used to investigate the dipole and quadrupole noise. Finally, the acoustic analogy method with Ffowcs Williams and Hawkings (FW–H) equation is adopted to study the far-field radiated noise features. Results reveal that during the acceleration process, vortex, vorticity and turbulent kinetic energy are generated at the leading edge of hydrofoil, and present corresponding shedding characteristics. Results also reveal that vortex, turbulence and noise are correlated at t = 2.4. For the distribution of vortex, turbulence and noise on the middle longitudinal section, there exists a strong correlation between turbulent kinetic energy (TKE) and Proudman Acoustic Power (AP). The relationship between vorticity and Proudman AP and TKE is complex, which is closely related to the generation, development and shedding of vorticity. Moreover, the distribution and development of Curle dipole noise sources on the suction surface are symmetrical. The directivity curve of the overall sound pressure level (OASPL) presents a butterfly-shaped symmetrical distribution. With the increase of accelerated time, the OASPL of most monitoring points gradually increases. Through the analysis on the spectral curves of vorticity, TKE, near-field and far-field characteristics, it is indicated that these quantities have a strong spectral correlation, which share the same peak frequency.