基于IBM-LES的贯流泵湍流特性

Turbulence characteristics of a tubular pump based on IBM-LES simulation

为充分了解贯流泵运行工况下的内部流动特性,通过基于浸没边界法的大涡模拟(IBM-LES)方法,研究了圆柱坐标系下某贯流泵在设计工况的三维非定常湍流流场.模拟基于三维笛卡尔网格坐标系,空间离散采用有限差分格式,时间推进采用二阶龙格库塔法,大涡模拟采用动态亚格子应力模型.采用水平集法描述流体中流道、叶轮、导叶等固体区域边界.结果表明:靠近叶轮叶片根部圆周截面的整体湍动能较弱,而在中等跨度圆周截面区域湍动能最大的位置位于叶轮叶片尾流区域,两处湍动能均主要由流向方向分量提供.叶轮叶顶间隙涡区域湍动能强度较大,且3个方向分量贡献相当.而在后置导叶尾流中,随着流向距离的增大和湍流的耗散与发展,尾流会逐渐发展而表现出均匀的圆管流动特性.研究结果可为改善贯流泵运行稳定性提供理论参考和工程应用支撑.

In order to fully understand the internal flow characteristics of tubular pumps under operating conditions,the turbulent flow of a tubular pump under the designed condition simulated by computational fluid dynamics(CFD)technology and immersed boundary method based large-eddy si-mulation(IBM-LES)was studied.The simulation was based on 3D Cartesian grid system,the Navier-Stokes equations were discretized by a finite difference method in space and advanced in time using a second-order Runge-Kutta method.The LES was applied with dynamic Smagorinsky model.Boundaries of solid parts were described by level set function.The result shows that the turbulence kinetic energy(TKE)is weak on the circumferential section across the root of impeller blades.The highest TKE is located at the wake of rotating impeller blades on the midspan section and the component in streamwise direction contributes most of the TKE.The TKE near the tip clearance of impeller blade is strong and contributed by components in three directions evenly.At the wake of outlet guide vanes,the turbulence dissipates and developes along the streamwise distance,the wake tends to exhibit the characteristics of pipe uniform flow.The results provide theoretical supports and engineering operation references for stability improvement of tubular pumps.