Analysis of Heat Transfer and Flow Over a Backward Facing Step

Abstract

Abstract Flow over a backward facing step along with heat transfer is studied for two and three dimensional vertical as well as curved backward facing step using ANSYS Fluent. The mesh is generated using ICEM software in ANSYS. The grid independency test is performed to make the results independent of the grid size after a particular number of elements. The reattachment length and Nusselt number are calculated for a wide range of Reynolds number covering both laminar and turbulent flow. The results obtained in the present study have been validated with published literature. Also the reattachment length and Nusselt number are calculated for various expansion ratios. The reattachment length is observed to decrease with increase in the expansion ratio for laminar flow whereas reattachment length is found to be increasing with increase in the expansion ratio for turbulent flow when expansion ratio is varied by changing the inlet channel height. The reattachment length is found to be increasing with expansion ratio for all laminar, transition and turbulent regimes when expansion ratio is varied by changing the step height. The reattachment length is also found to be less for curved backward facing step as compared to the vertical backward facing step. The results for the Nusselt number are calculated for wide range of Reynolds number incorporating both the laminar and turbulent flow. The value of Nusselt number is observed to increase with the Reynolds number both in laminar and turbulent case. The steep increase in the Nusselt number is found as we stepped into the turbulent flow at Reynolds number 2500. The results for Nusselt number are also compared for vertical backward facing step and curved backward facing step. The peak of the Nusselt number is observed to be shifted towards left for the curved backward facing step as compared to the vertical backward facing step due to decrease in the reattachment length for the curved backward facing step. The various flow characteristics are also obtained for vertical as well as for the curved backward facing step for laminar as well as turbulent flow. The results obtained from the curved backward facing step are compared with the vertical backward facing step.