Numerical and Experimental Investigation of the Flowfield Near a Wrap-Around Fin

摘要

A wall-mounted semi-cylindrical model fitted with a single wrap-around fin (WAF)has been investigated both numerically and experimentally, with the objective of characterizing the mean and turbulent flowfield in the vicinity of the fin. Numerical and experimental results are used to determine the nature of the flowfield and quantify the effects of fin curvature on the character of the flow near WAFs. This research has been motivated by the need to identify possible sources of a rolling moment reversal observed at high speeds in sub-scale flight tests. Detailed mean flow and turbulence measurements were obtained in the AFIT Mach 3 wind tunnel using conventional probes and cross wire hot film anemometry at a series of stations upstream of and aft of the fin shock/boundary layer interaction. Hot film anemometry results showed the turbulence intensity in the fuselage boundary layer to be far greater on the concave side of the fin than on the convex side. Similarly, the Reynolds shear stress rises dramatically on the concave side of the fin and is reduced on the convex side. These results are consistent with the stabilizing and destabilizing effects of pressure gradient distortion on supersonic boundary layers. Mean flow was also obtained in the AFIT Mach 5 wind tunnel using conventional pressure probes. Shadowgraph and schlieren photography were used for flow visualization in both wind tunnels.