Average Crossflow Velocity in Laminar Flow Systems with Periodic Finned Surfaces

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Abstract

Experimental and CFD studies of the enhanced average crossflow velocity in a laminar flow system were performed. The experiments were carried out using working fluid with a kinematic viscosity of 1.8·10–6 m2/s. A steady flow Reynolds number in the laminar range of 0 < Re < 400 and oscillation Reynolds number in the range 0 < Reosc < 1000 were studied. The range of oscillation amplitude and frequency were 0.2 mm < A < 1.0 mm and 5 Hz < f < 90 Hz respectively. Three experimental configurations were studied, i.e., oscillating finned surface in a fluid at rest, which is similar to a batch configuration, steady finned flow and oscillating finned flow configurations. The acquired images were analyzed using particle image velocimetry (PIV) software. The study is also supported by CFD simulations using the software suit CFX 11.0 from ANSYS GmbH, Germany. The results of the flow visualization and PIV analyses reveal the formation of periodic vortices and increased transverse transport. The maximum enhancement of the average crossflow velocity was obtained at κ = 3. The oscillation parameters and shape of the fins have a significant influence on the flow patterns and the crossflow effects. A triangular finned geometry gives better performance considering the enhanced average crossflow velocity. In general, efficient fluid mixing is possible due to the complex flow structures generated.

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