EFFECT OF AIDING BUOYANCY IN CONFINED FLOW OF POWER-LOW FLUIDS ACROSS A CIRCULAR CYLINDER

Abstract

Considerable efforts have been made to explore the rates of heat and momentum transfer across cylinders immersed in power-law fluids across a circular cylinder because of their wide range applications such as in heat exchangers, solar heating systems, natural circulation boilers, dry cooling towers. nuclear reactors, etc. This simple flow configuration displays wide variety of flow phenomena depending on various factors like nature of flow (laminar, turbulent, non-uniform, uniform), shape and size of body (circular or non-circular), fluid behavior, flow configuration, number of obstacles and their arrangement approaching flow condition (inline or staggered), the range of kinematic parameters, etc. When a fluid flows around bluff bodies, three shear layers interaction occurs i.e., a boundary layer, separating layer and wake. Flow unsteadiness induced by bluff-bodies enhances heat and mass transfer between the body and its surroundings. Wakes form behind bluff body as a result of flow separation and formation of recirculation zones occurs. The flow becomes more complicated when the wake is further influenced by heat transfer (Gandikota et al. 2010). The buoyancy effects are significant at low velocity and at large temperature difference between body and the ambient fluid. The buoyancy parameter (Ri = Gr/Re2), measures influences of free convection compared to the forced convection. Ri→0, denotes forced convection regime whereas Ri→∞ denotes free convection. Whereas Ri = 1 indicates mixed convection.