LAMINAR CROSS-BUOYANCY MIXED CONVECTION AROUND A CONFINED TRIANGULAR BLUFF BODY

Abstract

The study of combined free and forced (or mixed) convection around different geometrical bluff bodies in an enclosure has been a topic of considerable attention of researchers in recent times due to its fundamental and pragmatic relevance. It is one of most important subjects that has been studied both numerically and experimentally. The bluff bodies when placed in different fluid streams, generate different kind of fluid flow separation over a substantial portion of their surfaces, depending on their shapes. For example, the separation of the fluid flow occurs from fixed points in an edged cylinders (triangular and trapezoidal cross-section etc.) whereas for cylinders having continuous surface curvature ( circular or elliptical cross-section etc.), the flow separation depends on the shape of the bluff body and the state of boundary layer generated. The application of these studies has proven to be of great importance in understanding the effects of various parameters on the performance of thermal equipment in various engineering applications. These include heat exchangers, solar heating systems, boilers based on natural circulation, dry cooling towers, nuclear reactors , off-shore structures and flow metering devices etc. Similar other related problems and their studies have found applications in crop dryers, energy storage devices, crude oil storage tanks and flow dividers. The studies of researchers reveal that there exist lot of parameters which directly affect the heat transfer and flow patterns of the systems including obstacles or bluff bodies. Some of the important parameters include the nature of fluid (Newtonian or non-Newtonian), the shape of the bluff body, Reynolds number of the fluid, the blockage ratio, aspect ratio of the bluff body etc. The vast literature is available highlighting the study of forced and/or mixed convection across different shaped bluff bodies in enclosures with either cross buoyancy or aiding buoyancy flow and heat transfer with either vertical or the horizontal imposed heat flux/temperature difference. The present study has been taken up to find a correlation to report the mixed convection heat transfer and fluid flow under laminar cross-buoyancy over a heated equilateral triangular cylinder (aspect ratio=1) in a channel (horizontal) for laminar range of Reynolds numbers and other parameters for which no data is available. This study has been carried out for a fluid with constant Prandtl number of 0.71(air). The objective is to investigate numerically the effects of wall confinements on the flow and mixed convection from an equilateral triangular bluff body for laminar flow regime. The study also includes the