Numerical Simulation of Cavitating Water Jet by a Compressible Mixture Flow Method
Numerical Simulation of Cavitating Water Jet by a Compressible Mixture Flow Method
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DOI：
10.1299/jfst.6.499
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发表时间：
2011
影响因子：
0.8
通讯作者：
G. Peng;S. Shimizu;S. Fujikawa
中科院分区：
文献类型：
--
作者：
G. Peng;S. Shimizu;S. Fujikawa
针对伴有强烈空化的高速水射流的数值模拟，将气泡空化的简化估计与灵活的可压缩流动计算过程相结合，提出了一种实用的可压缩混合物流动方法。将空化流的两相流体介质视为液体和气泡的混合物，并通过应用可压缩流体的雷诺平均纳维-斯托克斯方程计算混合物的平均流量，考虑气泡膨胀和收缩的影响。空化的强度通过气体体积分数来评价，气体体积分数由当前平均流场状态下气泡-液体混合物的压缩性决定。从收敛-发散喷嘴喷出的高速浸没水射流在不同的空化条件下进行处理。结果表明，收敛段的压力下降，空化最初发生在喉部后面靠近壁的低压区域。当空化数减少到0.1时，空化气泡的气体体积分数局部达到0.5，喉部附近剪切层产生的空化气泡沿射流周边向下游流动。在空化气泡的作用下，虽然喉部最大速度有所增加，但水射流的质量流量系数与无空化情况相比明显减小。
Concerned on the numerical simulation of high-speed water jet accompanied with intensive cavitation, a practical compressible mixture flow method is developed by coupling a simplified estimation of bubble cavitation and a flexible compressible flow computation procedure. Two-phase fluid media of cavitating flow are treated as a mixture of liquid and bubbles, and the mean flow of the mixture is computed by applying Reynolds Averaged Navier-Stokes equations for compressible fluids considering the effect of bubble expansion a/o contraction. The intensity of cavitation is evaluated by gas volume fraction which is governed by the compressibility of bubble-liquid mixture at the current status of mean flow field. High-speed submerged water jets issuing from a convergent-divergent nozzle are treated under different cavitation conditions. The results demonstrate that pressure decreases in the convergent section and cavitation occurs initially in the low-pressure region behind the throat near the wall. The gas volume fraction of cavitation bubbles reaches to 0.5 locally when the cavitation number is decreased to 0.1, and cavitation bubbles generated in the shear layer near the throat flow downstream along the jet periphery. Under the effect of cavitation bubbles the mass discharge coefficient of water jet decreases obviously compared to the case of no-cavitating one although the maximum velocity at the throat increases.