运用三维动网格技术模拟计算离心泵的非定常流动

 运用三维动网格技术,对离心泵非定常流场进行数值模拟。使用Fluent流动软件的Profile文件定义叶轮计算域边界面的转向和转速,将所有计算域设在同一个惯性系中。采用弹簧光滑法、动态分层法及局部网格重构法3种方式实现计算域网格变形。在同样的计算模型、计算网格、初始条件、边界条件及软件设置条件下,将动网格与传统的滑移网格计算结果进行了对比。计算结果显示:在经历约5个叶轮旋转周期后,两种计算网格数值结果趋于一致,但动网格的迭代速度几乎是滑移网格迭代速度的3倍。原因是动网格计算仅在一个惯性系中进行,新旧网格节点的拓扑关系保证了良好的计算精度和时间上的连惯性;而滑移网格计算因多参考系之间的数据对接影响了时间上的连贯性、降低了迭代速度。研究表明采用动网格技术可实现水泵的三维非定常流场数值模拟,具有较强的通用性和广阔的应用前景。

Numerical Simulation of 3D Unsteady Flow in Centrifugal Pump by Dynamic Mesh Technique

The 3-D dynamic meshing technique is applied for the numerical simulation of unsteady flow fields in a centrifugal pump using the Fluent software. The surface motion of the impeller in the computational domain is defined by the profile file in the Fluent software, in which the rotational direction and the speed of the impeller are specified. The simulation results are compared with those obtained by the widely used sliding mesh technique to illustrate the superior computational efficiency of the dynamic mesh method. In the dynamic mesh technique, all computational domains, considered as stationary, are defined in an inertial reference frame, while the topological relationships between the previous and the current mesh nodes are retained to ensure a good precision and time coherency. Three methods, namely the spring-based smoothing, the dynamic layering and the local re-meshing are used to cope with mesh deformations. Comparisons of solutions with those obtained by using the sliding mesh technique with an identical computational model, the same meshes, and initial and boundary conditions show that the results of both methods converge to comparable solutions within five revolutions of the impeller. The iterative speed of the dynamic mesh method, however, is almost three times of that of the Sliding Mesh method. The results thus suggest that the dynamic mesh technique for the flow simulation in centrifugal pumps, defined in an inertial reference frame, yields a substantially better computing efficiency than the sliding mesh method involving a comprehensive data transfer among multiple reference frames. This work shows that dynamic mesh technique can be used for numerical simulations of a three-dimensional unsteady flow field in pumps and has a strong versatility and broad application prospects.