Influence of thermal buoyancy on boundary layer separation over a triangular surface

We endeavour here to elucidate the role of the superimposed thermal buoyancy on the boundary layer separation over a two-dimensional triangular surface. Particular emphasis is given to analyze the response of different orientations of the triangular object with respect to the incoming flow under the action of aiding/opposing thermal buoyancy. The object is placed in a vertical unconfined domain with two different orientations, one when the apex of the object is facing the flow (C1) and the other when one of the bases of the object is exposed to the incoming fluid (C2). A similar study by Chatterjee and Mondal (2014) considering circular and square shaped objects reveals that the steady, laminar and separated flow over the objects at low Reynolds numbers can be degenerated to an attached flow under the action of aiding thermal buoyancy. However, unlike circular/square bodies, the triangular body shows significant deviations in the separation characteristics. The present effort aims at numerically obtaining the critical heating parameters for which the separated boundary layer on the triangular object can be suppressed and analyzing the influence of the object orientation on the thermally induced suppression phenomena. Furthermore, the opposing buoyancy is known to trigger the vortex shedding process at low Reynolds numbers which is already established for circular/square objects. This triggering of vortex shedding over different orientations of a triangular object under the action of opposing buoyancy is numerically demonstrated. The Reynolds number is kept in the range 5 ⩽ Re ⩽ 30 keeping the Prandtl number fixed at Pr = 50 with varying Richardson number. The critical Richardson numbers for the onset of flow suppression as well as the complete suppression of flow separation and the critical Richardson number for the onset of vortex shedding are obtained for the two different orientations of the object. Important inferences are drawn on the fluid dynamic and thermal transport characteristics focussing the separation phenomena. It is observed that the configuration C1 needs more heating than C2 for flow suppression. Also, C1 needs more cooling than C2 for the initiation of the vortex shedding. Such quantification in regard to the critical heating parameters for flow suppression and triggering of vortex shedding over a triangular object is reported for the first time.