The flow and heat transfer characteristics in the region of an asymmetric contraction in a two-dimensional channel are studied numerically. The contraction is in the form of a step on one of the channel walls. Channel wall-to-wall spacing ranges from 2 step heights to 10 step heights, with Reynolds numbers, based on channel hydraulic diameter, ranging from 500 to 2500.
Separation and recirculation regions occur upstream from the contraction; the flow generally separates on the order of one step height upstream from the step and re-attaches approximately one-half the distance up the step face. In some cases there is a recirculation region on the top of the step, beginning just downstream from the leading edge of the step, and typically a few step heights in extent. Heat transfer is reduced in the recirculation regions, relative to that of a parallel-wall flow. In addition, there is heat transfer augmentation on the wall opposite the step, not only because of the contraction itself, but also enhanced by the flow around the recirculation regions. Correlations are reported for friction factor and for heat transfer augmentation and reduction, and results are reported for location of separation and reattachment points and for heat transfer across the entire region.