绕水翼非定常空化流场数值模拟

Numerical simulation of unsteady cavitating flow around hydrofoil

基于Reynolds平均法,采用RNG k-ε模型及Mixture两相流模型,对绕攻角10°的ys930水翼非定常空化流动进行了数值模拟,分析了空化数分别为1.0,0.8,0.5时的空化流场结构、流动特性及空泡演化过程等.结果表明:云状空泡由两部分组成,前一部分为空泡主体,稳定附着于水翼吸力面上,其内部充满水蒸气,压力为汽化压力;后一部分为空泡附体,为周期性气液两相运动区域.空泡前端位置基本稳定,空泡主体长度随时间变化先增大后减小;空泡主体长度由空化数和回射流强度共同决定.空泡厚度随时间变化先增大后减小,空化数越小,空泡能达到的最大厚度越大,同时最大厚度出现位置越靠近水翼尾缘.回射流的强度与空化数成反比,空化数越小,回射流强度越大,来流与回射流的相互作用决定了空泡附体脱落的位置.

Based on the Reynolds time-ave raged N - S equations, the unsteady cavitating flow around ys930 hydrofoil was simulated by the RNG k -ε turbulence model and the mixture two-phase caviatation model. The characteristics of unsteady cavitating flow and the cavity evolution process around the hydrofoil at a 10 deg attack angle at three cavitation numbers 1.0, 0.8 and 0.5 were obtained. The results show that there are two parts in a cavity, the front part is attached to the suction surface of the hydrofoil and full of water vapor. The rear part is the periodic, unsteady, collapsible two-phase flow zone. The attaching point of the front part is basically stable, the length of the cavity initially is in- creased, subsequently decreased. The length is decided by cavitation number and strength of re-en- trant jet simultaneously. The thickness of the cavity firstly rises, and then is reduced. The smaller the cavitation number, the closer to the trailing edge of the hydrofoil the maximum thickness location. The strength of re-entrant jet is inversely proportional to cavitation number, the smaller the cavitation number, the lower the strength of re-entrant jet. Moreover the position of the detaching point of cavity is determined by the interaction between the coming flow and the re-entrant jet.