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FLOW STRUCTURES AND HEAT TRANSFER ON DIMPLED SURFACES

Johann Turnow
Chair of Modeling and Simulation, Department of Mechanical Engineering and Marine Technology, University of Rostock, Albert-Einstein-Str. 2, 18055 Rostock, Germany

Valery L. Zhdanov
Department of Technical Thermodynamics, Rostock University, A. Einstein Str. 2, Rostock, 18059, Germany

Nikolai Kornev
Chair of Modeling and Simulation, Department of Mechanical Engineering and Marine Technology, University of Rostock, Albert-Einstein-Str. 2, 18055 Rostock, Germany

Egon P. Hassel
Institute for Technical Thermodynamics Faculty of Mechanical Engineering and Marine Technology University of Rostock Albert-Einstein-Str. 2, D-18059 Rostock, Germany

Sinopsis

Vortex structures and heat transfer enhancement mechanism in a turbulent flow over a staggered dimple array in a narrow channel have been investigated using Large Eddy Simulation (LES), Laser Doppler Velocimetry (LDV) and pressure measurements for ReD = 10000 and ReD = 20000. The flow and temperature fields are captured by LES using dynamic mixed model applied both for the velocity and temperature. Simulations are validated by comparison with experimental data obtained for smooth and dimpled channels. Experiments and LES show that the time averaged fields are symmetric in spanwise direction for each dimple. The flow inside of the dimple is chaotic and consists of small eddies with a broad range of scales where coherent structures are hardly to detect. For both Reynolds numbers it was found that the dimple package with the depth t to diameter D ratio of t/D = 0.26 provides the highest heat transfer and thermo-hydraulic performance. Proper Orthogonal Decomposition (POD) method is applied to resolved LES fields to identify spatial-temporal structures hidden in the random fluctuations of pressure and velocity fields.