绕弹性水翼空化流激振动特性实验研究

Flexible structures are prone to vibrate under cavitation loads, threatening the safety of structures. Therefore, it is important to analyse the cavitating flow induced vibration around flexible hydrofoils. A high-speed camera, a Laser Doppler Vibrometer (LDV), and a hydrodynamic load cell are exploited to observe the cavitation structures, measure the hydrofoil vibrations, and measure the lift and drag static forces, respectively. The load coefficients of the flexible hydrofoil keep constant in the sub-cavitation stage, while they first increase then decrease with the decay of the cavitation number in the cavitating flow. The probability density functions of vibration velocities in the incipient cavitation, sheet cavitation, and cloud cavitation stages are all Gaussian. The vibration velocity of the hydrofoil has the largest amplitude and root-mean-square in the cloud cavitation stage and varies periodically due to the periodic shedding and collapse of the large-scale cloud cavitation. The re-entrant jet and shockwave shedding are the two main shedding mechanisms in the cloud cavitation stage. Similarly, the evolution of the cloud cavity induced by the shockwave mechanism can be divided into four stages: 1) the attached cavity growth; 2) the re-entrant jet development; 3) the shedding and collapse of the cloud cavity; 4) residual cavity collapse. The vibration induced by the re-entrant jet mechanism has small amplitude and high frequency, while the opposite is true for that induced by the shockwave mechanism due to the collapse of the large-scale cavity and the subsequent secondary collapse of the attached cavity.