INFLUENCE OF AN ADIABATIC SQUARE CYLINDER ON HYDRODYNAMIC AND THERMAL CHARACTERISTICS IN A TWO-DIMENSIONAL BACKWARD-FACING STEP CHANNEL

The work demonstrates numerically the influence of an adiabatic cylinder of square cross section on the flow and heat transfer characteristics within a two-dimensional backward-facing step channel. The study was conducted for a Reynolds number range of 1-200 (in the steady laminar regime) with a fixed Prandtl number of 0.71 (air). Additionally, simulations are also conducted for Reynolds numbers of 104 and 2.10(4) (unsteady turbulent regime). The numerical simulation is performed by deploying a finite volume-based commercial solver FLUENT. Different cross stream positions of the cylinder are considered to show the positional effect of an obstacle on the overall flow and heat transfer pattern. The flow and thermal fields are demonstrated through the streamlines and isotherm profiles for different Reynolds numbers and cylinder positions. The global flow and heat transfer quantities such as the reattachment length, drag coefficient, local and average Nusselt numbers are computed and presented. A significant heat transfer augmentation due to the presence of the cylinder is observed as compared to the unobstructed case (without a cylinder). Furthermore, it is observed that the heat transfer augmentation is stronger for the case of a square cylinder in comparison with a circular one introduced into the same channel. Finally, correlations are devised for the drag coefficient and Nusselt number for the above range of conditions.