Heat Transfer From an Open- or Closed-Bore Cylinder Situated Longitudinal to a Freestream

Wind tunnel experiments were performed to determine the local response of the heat transfer at the outer surface of a longitudinal cylinder to geometry-related differences in the pattern of fluid flow. Among the three investigated configurations, one was a cylinder with an open bore through which fluid could pass, while in the second the bore was closed at its downstream end, creating an upstream-open-ended cavity. In the third configuration, the upstream face of the cylinder was impenetrable and blunt. The Reynolds number ranged from 7700 to 47,000. For all cases, the axial distribution of the Nusselt number was characterized by an initial increase, followed by the attainment of a maximum and a monotonic decrease, reflecting the occurrence of flow separation and of post-reattachment boundary layer development. The magnitude and location of the maximum were configuration dependent, with that for the open configuration being highest and occurring first, and that for the blunt face configuration being lowest and occurring last; the cavity configuration gave intermediate results. Upstream of the maxima, the Nusselt numbers were arranged in the same order as at the maximum, with a configuration-related spread of 50 percent. Well downstream of the maxima, the ordering was reversed and the spread was in the 5 percent range. Tight, configuration-independent correlations were achieved both for the maximum Nusselt number and for the Nusselt numbers in the downstream region.