轴流式喷水推进泵内涡与空化相互作用

Investigation on the mechanism between vortex and cavitation in an axial waterjet pump

喷水推进泵内空化的发生直接影响推进效率,尤其是进入性能陡降工况,针对目前对该工况下喷水推进泵内涡与空化相互作用认知不足,极需从机理方面展开研究。本文采用分离涡流模拟(detached eddy simulation,DES)湍流模型Zwart-Gerber-Belamri(ZGB)空化模型对性能陡降工况下的喷水推进泵内部空化流场进行数值模拟,并结合柱坐标系下的涡量输运方程对喷水推进泵内涡与空化的相互作用机理进行分析。研究表明:数值计算的空化性能曲线与实验测量结果吻合较好;涡线拉伸扭曲项与涡量分布密切相关;斜压矩项和膨胀项主要集中在汽液交界面处,会引起涡量场的重新分布,并且膨胀项的量级要大于斜压矩项;在间隙处,粘性耗散性量级较大,粘性耗散项的作用不可忽略。

Cavitation in a waterjet pump directly affects the propulsion efficiency,especially in the case of a hydraulic performance breakdown.At present,due to the fact that the interaction between vortex and cavitation in waterjet pumps is not fully understood under such working conditions,an in-depth research on this specific mechanism must be carried out.In this study,the detached eddy simulation(DES)turbulence model and the Zwart-Gerber-Belamri(ZGB)cavitation model were used in order to simulate the cavitating flow in the waterjet pump under the critical working conditions,when the performance drops sharply.The vorticity transport equation with a cylindrical coordinate system is employed in order to study the vortex-cavitation interaction in waterjet pumps.The results show that the cavitation performance curve of the numerical calculation agrees quite well with the available experimental results.The Vortex stretching term is closely related with the distribution of vorticity.The vortex dilation term and the baroclinic torque term appear mainly at the vapor liquid interface,which causes the redistribution of vorticity.The magnitude of the vortex dilation term is larger than that of the baroclinic torque term.In the blade tip region,the magnitude of the viscous dissipation term is larger and the effect of this term cannot be neglected.