Some studies on transport phenomena in presence of a bluff body

Abstract

Transport phenomena around bluff bodies have been a subject of considerable research interest. Heat transfer characteristics inside a channel in presence of bluff body and effect of turbulence level on transport process around bluff bodies encompassing laminar and turbulent regime covering a Reynolds number range of 10-2,00,000 along with turbulence intensities varying from 5 per cent to 40 per cent are studied in this work. Here bluff bodies of five different shapes are considered, namely-a) Circular cylinder, b) Square cylinder, c) Equilateral triangular prism, d) Diamond and e) Trapezium shape bluff bodies. The effect of turbulence intensity on the transport phenomena over two-dimensional bluff bodies is investigated. The governing equations of continuity, momentum, and energy equations are solved along with transition SST Model for the closure of turbulence. The simulation results are validated with experimental correlations which show good agreements. This work demonstrates that the transition SST Model can effortlessly bridge all flow regimes for predicting the heat transfer. The study quantifies the effect of inlet turbulence intensity on enhancing heat transfer from the bluff bodies. The drag and pressure coefficients are found to be unaffected by inlet turbulent intensity. An operative study of different bluff bodies is incorporated in this work. The flowing medium i.e., the air is considered to have a constant Prandtl number (0.71). This work explains that transition SST Model can effortlessly link all flow regimes for predicting the heat transfer. The study quantifies the effect of inlet turbulence intensity on improving heat transfer from different bluff bodies. As part of the present work, an attempt has been made to study augmentation of heat transfer on a channel wall in the presence of the bluff body of different shapes. Heat transfer enhancement in a channel in presence of bluff bodies of different shapes has been numerically investigated in the turbulent flow regime with Reynolds number ranging from 100-2,00,000. The hydraulic diameter of the bluff body (Three different shapes namely Triangular Prism (TP), Diamond, and Trapezoidal are considered in this work) is taken as characteristic length. The inlet turbulent intensities are varied from 5 per cent to 40 per cent. The aspect ratio between channel to the bluff body is fixed at 4. The velocities and pressures were predicted using semi-implicit pressure linked equations (SIMPLE) scheme. The study quantifies the effect of inlet turbulence intensity on enhancing heat transfer from all other bluff bodies. Augmentation is associated with higher values of skin friction coefficient on the channel wall. The Augmentation is also expressed as a percentage increased of heat transfer from a similar system without the diamond bluff body.