水翼表面布置射流水孔抑制空化

为研究水翼表面布置射流水孔对空化的抑制效果,采用RNG k-ε湍流模型结合全空化模型对8°攻角NACA0066(MOD)水翼进行二维非定常空化流场计算,分析当射流比分别为0.1,0.2和0.3时的水翼表面空化流场结构及其演化过程的流动特性,得到了不同射流条件下水翼升阻力系数的变化趋势.计算结果表明:布置射流水孔可以有效阻挡回射流从翼型尾部向翼型头部的运动,使得空泡脱落现象明显减弱,从而抑制了片空化向云空化的发展,且随射流比增加,射流对回射流和云空化的抑制作用更加显著;射流的注入同时使得升力系数和阻力系数的波动幅度明显降低,有效减弱了升阻力的周期性振荡;虽然时均升力和时均阻力受射流的影响有下降趋势,但升阻比呈上升趋势,水翼升阻比由无射流孔时的6.11增加到射流比为0.3时的7.06,布置射流孔还起到了减阻的作用.

Impact of hydrofoil surface water injection on cavitation suppression

To study the effectiveness of hydrofoil surface water injection on cavitation suppression, the unsteady cavitating flow around a 2-D NACA0066(MOD)hydrofoil at attack of 8° was simulated by RNG k-ε turbulence model combined with the full-cavitation model with the jet-flow ratio at 0.1, 0.2, 0.3, respectively. The structure of unsteady cavitating flow and the trend of lift and drag coefficients were obtained. Results show that water injection can barrier the reentrant jet rushing from the trailing edge to the leading edge of the foil so as to thus weaken the frequency of bubble shedding, thereby suppressing the development of sheet cavitation to cloud cavitation. With the increase of jet intensity, the inhibition of reentrant jet and the suppression effect of cloud cavitation is more significant. The fluctuation amplitudes of lift and drag coefficients are reduced, thus weakening the periodic oscillation of force on the hydrofoil surface. Although the time-averaged lift and drag coefficient show a downward trend, the lift-drag ratio has a rising trend. The lift-drag ratio increases from 6.11 with non-injection to 7.06 at the jet-flow ratio of 0.3, and the layout of water injection hole has the effect of drag reduction.