A classical configuration in thermal engineering is the rectangular cavity that is differentially heated over two opposing vertical walls. In this paper, the instability mechanism responsible for the transition from steady to time-periodic flow in both two and three-dimensional cavities with perfectly conducting horizontal walls is studied. For both air (Pr = 0.71) and water (Pr = 7.0), the instability is a thermal instability resulting from an unstable stratification in the boundary layers along the horizontal cavity walls. The frequency is in good agreement with the frequency predicted using Howard’s model (1966). For air, the perturbations arise at fixed depths in the cavity whereas for water they travel along the hot and cold walls of the cavity.

Issue Section:
Natural and Mixed Convection
Keywords:
Enclosure Flows, Flow Instability, Natural Convection
Topics:
Cavities, Flow (Dynamics), Water, Boundary layers, Cavity walls, Flow instability, Natural convection, Thermal engineering
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