Numerical investigation of the influence of the tip clearance flow and the Coriolis force on the near wal flow in a compressor stage

目前涡轮机械中增加压力比、减少叶片数、减小展弦比、剧烈的部分负荷运行等努力导致了侧壁附近流动对发动机整体性能的影响越来越大。特别是工作范围、损失和传热受到这些流动的影响。虽然经过几十年的研究，但发生的机制尚未完全理解。因此，当前的技术进步强烈要求充分的基础研究活动。这一缺陷将由德累斯顿工业大学、慕尼黑大学和波鸿大学四个研究小组的联合研究计划来解决，通过仔细协调模拟和实验来产生相关结果。除了研究传热和开发有条理的工具外，这个联合项目的一个主要目标是详细分析系统旋转的影响。因此，一些特别规划和调整的配置将被调查和相互比较。在这个联盟中，德累斯顿工业大学流体力学主席项目的目的是双重的。一是研究侧壁附近二次流的物理特性，并将其与线性叶栅中的情况进行对比。二是为涡轮机械栅格提供可靠的湍流分辨仿真技术。物理问题将与DNS和LES一起进行调查，以便在合作项目中进行实验研究，从而确保可靠的验证。这些复杂且控制良好的模拟可以产生非常丰富的数据，例如，提供有关过渡过程的信息。通过模拟有旋转和没有旋转的配置，可以研究近壁流动对流入条件的依赖关系，以及系统旋转产生的影响，如科里奥利力、桨距随叶片高度增加、径向压力梯度、端壁的相对运动和入口边界层的剪切。工作的方法论导向部分涉及可视化和后处理，主要是LES的子网格尺度模型和墙模型的评估和开发。事实上，对这种类型的改进模型有很大的需求，这种模型很好地适用于涡轮机械流动。对获得的模拟数据的分析将与项目合作伙伴一起进行，比较相同配置的不同方法的结果-如实验，URANS， LES -或不同配置的结果，其中压气机和涡轮流量的比较，因此涵盖了非常广泛的参数范围。

Current efforts in turbomachinery to increase pressure ratio, reduce blade count, decrease the aspect ratio, intense part load operation, etc. lead to increasing influence of flows near the side walls on the overall engine performance. Especially the operating range, losses and heat transfer are influenced by these flows. The occurring mechanisms are not fully understood although being investigated since decades. Thus the current technological progress strongly requests adequate basic research activity. This deficit will be addressed by a joint research program of four research groups at TU Dresden, UniBw München und RU Bochum, by carefully coordinated simulations and experiments to produce relevant results. Beside the investigation of heat transfer and the development of methodical tools a major goal of this joint program is the detailed analysis of the effect of system rotation. Therefor a number of specially planed and adjusted configurations will be investigated and compared with each other.Within this consortium the purpose of the project at the Chair of Fluid Mechanics, TU Dresden, is twofold. One is to investigate the physics of the secondary flow near the side walls and to contrast it with the situation in a linear cascade. The other is to contribute to a reliable turbulence-resolving simulation technology for turbomachinery grids. The physical issues will be investigated with DNS and LES for configurations experimentally investigated in partner projects, thus insuring reliable validation. These involved and well controlled simulations can yield very rich data and, for example, provide information about transition processes. Simulating configurations with and without rotation will allow studying the dependence of the near-wall flow on inflow conditions and effects generated by the system rotation, such as Coriolis force, increasing pitch with blade height, radial pressure gradients, relative motion of the end walls and shear of the inlet boundary layer. The methodologically oriented part of the work are concerned with visualization and post-processing and predominantly with assessment and development of subgrid-scale models and wall models for LES. Indeed, there exists a large demand for improved models of this type well applicable to turbomachinery flows. The analysis of the simulation data obtained will be conducted with the project partners comparing results of different methods for the same configuration - like experiment, URANS, LES - or results for different configurations among which comparisons between compressor and turbine flow thus covering a very wide parameter range.