Heat Transfer to Separated and Reattached Subsonic Turbulent Flows Obtained Downstream of a Surface Step

Local heat-transfer coefficients and recovery factors are presented for separated and reattached turbulent flows as obtained by a downward step in an otherwise flat surface in a two-dimensional, subsonic, air flow. The region downstream of the step, the focus of this investigation, contained a region of separated flow with reattachment at about five step heights downstream, followed by a section of reattached flow. The salient feature of the results is the maximum in the local heat-transfer coefficient at the reattachment point, with values thereof diminishing in the separated region and also in the reattached region, where they tend toward values characteristic of turbulent boundary-layer flow. I t is found that for most of the region the heat-transfer coefficient depends on the velocity to about the 0.8 power, though a decreased dependence may exist in the separated region. Recovery factors have the characteristically low values associated with separated flows, and do not attain values typical of turbulent boundary-layer flows within the downstream lengths available.