Transonic Merging Separated Flows

摘要

This study considers an arrangement of a plane-nosed circular cylinder with a smaller diameter plane-nosed cylindrical probe coaxially extending ahead in a transonic axial flow. This configuration is a prototype for a low drag forebody replacing more conventional streamlined nose fairings. Apparently only one previous study is available in open literature which clearly shows reductions in transonic forebody drag for such arrangements. In view of the lack of data on transonic flow past probe/cylinder configurations, an attempt is made to construct the flow field based on data for related and component flows. The flow is modelled as the merging of several component, separated flows. Component flows are axisymmetric plane-nosed cylinders and axisymmetric forward-facing steps. Related flows include rearward-facing steps, cavities and bases. Relatively little data are available in the open literature concerning transonic flow past any of these arrangements, especially for axisymmetric geometries. The data which is available is discussed for insights which might be gained regarding probe/cylinder flows; emphasis is given to a plane-nosed cylinder flows and the opening phenomenon associated with cavity flows. A simple, semi-empirical free streamline model is developed for the postulated flow field of a low-drag probe/cylinder configuration. Partial agreement with inferences from related experimental data is obtained.