Investigation of Modeling Concepts for Plume-Afterbody Flow Interactions.

A high pressure hot gas supply system has been developed for the FFA 0.5 x 0.5 m S5 supersonic wind tunnel to allow the study of aerodynamic interference effects caused by plume induced flow separation on afterbodies. Capable of operating with gases covering a wide range of specific heat ratios, the facility serves to critically evaluate the merits and limitations of plume modeling techniques. The facility is now fully operational. Plume modeling experiments have been performed using air and Freon-22 for jet simulation at a free stream Mach number of 2.0 and zero angle of attack. One prototype air nozzle and two Freon nozzles modeled in accordance with the methodology suggested by Korst have been investigated. The Freon plume shapes have been found to be in close agreement with those of the corresponding air tests supporting the suggested modeling methodology and design procedures. The agreement between prototype and model base pressures was satisfactory not only for the design point but also for a rather wide range of off-design conditions. The more sensitive parameter, the location of the separation line on the conical afterbody, was equally well correlated but for a narrower range in the vicinity of the design point and only for the nozzle designed with the assumption of a weak shock closure condition. Author