抄録
Three-dimensional numerical simulation has carried out for a backward-facing step flow in a duct in order to see if intensive difference in flow and thermal structures has been generated for two different inlet velocity conditions between uniform flow and fully-developed flow. Although the maximum Nusselt numbers on the bottom wall appear near the side wall for both cases, the value of it in the fully-developed flow case shows much larger than that in the uniform flow case. Furthermore, owing to the strong complicated three-dimensionality of the flow and thermal structures, Nusselt number for the fully-developed flow especially shows no longer uniform value along the spanwise direction. Fresh downwash fluid near the side wall and its complicated swirl-like motion enhance heat transfer there, whereas, some part of the downwash fluid becomes hot while circulating many times behind the step an flows downstream from the centerline of the duct so that the Nusselt number decreases as it goesfrom the side wall to the duct centerline. It was found that such feature becomes much weaker for the uniform flow case in the present study.
