A FLOW VISUALIZATION STUDY OF THE FLOW IN A 2D ARRAY OF FINS

A study of the flow field in a 2 D arrangement of fins was carried out by means of flow visualization in a vertical water tunnel. A similar arrangement of fins had been tested as a conceptual heat sink, and the heat transfer measurement showed a dependence of the heat transfer qualities on the geometrical parameters of the fin's array. The current study examines the complex flow field structure in order to obtain a better understanding of the convection process. The model is built of several series of fins, generating a multi-cell structure. The investigation included a systematic variation of the fins' chord and inclination angle, as well as the flow velocity. Two main flow structures were observed. In the first one, the flow separates from the leading edge of each fin. Due to the influence of its neighbouring fins, the flow re-attaches to the fin, creating a closed separation zone. A vortex fills this separation zone. The main flow accelerates in the passage that is created between the separation bubble and the neighbouring fin. In the second flow structure, the flow separates from both leading and trailing edges of each fin. The separation is in alternating order and generates a nonsteady pair of vortices. This separation pattern is similar to that of a single plate at high angle of attack, and the effect of the neighbouring fins is only to narrow the wake. The pressure drop across the model was measured and correlated to a single nondimensional variable on a single curve.