LES and PTV Measurement of Turbulent Flow in Expanding Concentric Annular Flow-Passage with Rotating Inner-Wall

具有旋转内壁的环形流道广泛应用于工业设备中，例如离心机、径向轴承和旋转机械。因此，了解这类流动通道中的流动和换热是非常重要的，因为多种流动不稳定因素可以同时影响：由于贯通流动和/或内壁旋转引起的剪切流动不稳定性，以及由于周向和/或通流流线曲率引起的离心流不稳定。在实际应用中，大多数流动是湍流的，并且横截面沿直通方向发生变化，这使得现象更加复杂。本研究的目的是通过大涡模拟和粒子跟踪测速仪的测量来研究多种流动不稳定因素对湍流流动的影响。考察了两种类型的流道：凹型和凸型，以TH…的形状命名更多的是内墙。在PTV测量中，采用了两帧法，计算了时间平均速度和湍流强度。在实验中，尽管流动的雷诺数Re在1,000到10000之间变化，泰勒数Ta在0到8,000之间变化。当Re=1000时，内壁旋转导致下游区域湍流强度增大。当Re=10000时，上游和下游的湍流强度都增大。内壁旋转引起出口回流，大涡模拟在曲线坐标系下采用二阶有限差分方法进行。凹型和凸型通道被处理为Re=1000(常数)和Ta=0-4000。外围计算大小在45度、90度和360度之间变化。在大涡模拟结果中，进口附近的流动结构是均匀的，内壁的旋转在下游区域引起了湍流。旋涡结构取决于泰勒数、流道类型和流道位置(上游/下游和靠近内壁/外壁)。由于逆流和湍流的影响，换热系数的分布变得复杂。壁面剪应力和扭矩系数的检测进一步阐明了各流道内流动结构的差异。较少

An annular flow passage with a rotating inner wall is widely utilized in industrial apparatuses, and the examples are centrifuges, journal bearings, and rotating machinery. Therefore, the understanding of the flow and heat transfer in this type of flow passage is important In this flow passage, multiple flow-instability factors can simultaneously affect; shear flow instability due to through flow and/or inner-wall rotation and centrifugal flow instability due to peripheral and/or through-flow streamline curvatures. In the real applications, most of the flow becomes turbulent, and the cross-sectional area changes in the through-flow direction, which further complicates the phenomena. The objective of this study is to investigate the turbulent flow affected by the multiple flow-instability factors by performing Large Eddy Simulation (LES) and Particle Tracking Velocimetry (PTV) measurement.The two types of flow passages were examined : concave and convex types named after the shape of th … More e inner wall. In the PTV measurement, two-frame method was used, and the time-averaged velocities and the turbulence intensities were calculated. In the experiment, though-flow Reynolds number, Re, was varied from 1000 to 10000, and the Taylor number, Ta, was varied from 0 to 8000. For Re=1000, the inner-wall rotation caused the increased turbulence intensity in the downstream region. For Re=10000, the turbulence intensity increased in both the upstream and downstream regions. The inner wall rotation induced the reversed flow at the outlet.The LES was performed in the curvilinear coordinate system using the second order finite difference method. The concave-and convex-type passages were treated for Re=1000(constant) and Ta=0-4000. The peripheral computational size was varied among 45, 90, and 360 degrees. In the LES result, the flow structure was peripherally uniform near the inlet, and the inner wall rotation induced turbulence in the downstream region. The vortex structure was dependent on the Taylor number, the flow passage type, and the position in the passage (upstream/downstream and near inner/outer wall). The heat transfer coefficient profile became complicated due to the reversed flow and the turbulent transfer. The examination of wall shear stress and torque coefficient further clarified the flow structure difference in each flow passage. Less