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

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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