DMD and POD of time-resolved schlieren on a multi-stream single expansion ramp nozzle

Time-resolved schlieren measurements were conducted on a supersonic rectangular multi-stream nozzle used for three-stream engines. The jet utilizes a single expansion ramp nozzle (SERN) configuration along with an bypass stream, operating at an ideally expanded bulk flow of M-j,M-1 = 1.6 and bypass stream of M-j,M-3 = 1.0. Experiments were conducted with and without an aft deck to model airframe integration. Schlieren imaging was acquired up to 100 kHz in two different orientations. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) were applied to the schlieren data to identify flow structures. Comparisons were made between the two decomposition methods in the form of spatial correlations. (C) 2017 Elsevier Inc. All rights reserved.