Effect of an Extended Shelf on Near Field Development of Supersonic Jet Plumes from Rectangular Nozzles

Abstract

An experimental study is reported of underexpanded supersonic jet plumes issuing from a high aspect ratio rectangular nozzle. Schlieren visualisation, Pitot probe, and LDA measurements are made to capture the plume development in the near-field, and in particular the effect on the plume flow of the presence of a finite-length extended shelf (or aft-deck) attached to the lower wall of the nozzle. This creates asymmetry in inviscid shock cell patterns, entrainment, and shear layer growth, and induces a net pressure force on the aft-deck wall, which leads to transverse deflection of the jet plume. For sufficiently high Nozzle Pressure Ratios, and a sufficiently long shelf, separation (and possible reattachment) of the plume from the extended shelf wall is observed. Detailed mapping of both mean velocity and turbulence fields is carried out, enabling comparison of clean nozzle and nozzle with aft-deck near-field flow development to be made. The data provided are proposed as a suitable benchmark validation test case for CFD studies of rectangular nozzle plumes with aft-deck interaction effects.