Numerical simulation of flow and heat transfer around an octagonal bluff body

Abstract

Flow around bluff bodies have received attention of researchers over the years . In this work, transport phenomena around a octagonal bluff body has been numerically investigated.Heat transfer characterstics inside a channel in presence of bluff body and effect of turbulent intensity on transport process around a bluff body encompassing laminar and turbulent regime covering a Reynolds number range of 100 to 100,000 along with turbulent intensities varying from 5% to 40% are studied in this work. This work demonstrates that SST models can effortlessly bridge all flow regimes for predicting the heat transfer. It also quantifies the effect of inlet turbulence intensity on enhancing heat transfer from the cylinder. While transport phenomena in external flows over bluff bodies have been studied thoroughly, comparetively few works report flow and heat transfer studies over octagonal bluff bodies. The flow field around a bluff body and associated heat transfer are nevertheless important for design of power plant machineries. This work comprises of two parts. A geometry of bluff body has been designed and then, simulation is performed over the octagonal bluff body which includes laminar and turbulent regime in the Reynolds number ranges from 100–100,000.The governing equation has been solved are continuity, momentum and energy equations. Recent research (e.g. Abraham et al., 2009) has demonstrated that the transition SSST model developed by Menter et al. (2002) is able of properly connecting the laminar and turbulent regimes in the transition zone. Here, the turbulent viscosity is calculated to take the changing flow field into account. The addition of an intermittency parameter creates a divergence from the traditional two-equation model. This variable has a range of 0 to 1.0. The computation indicates a zero value of intermittency for a pure laminar regime. The Reynolds number in this work is based on the shape of the bluff body. It is assumed that the bluff body's surface temperature will always be lower than the temperature of the incoming fluid stream. There have also been computed for the steady and transient versions of the SST model in addition to laminar computing in the low Re region.