Proper orthogonal decomposition and dynamic mode decomposition of under-expanded free-jets with varying nozzle pressure ratios

Abstract

© Springer International Publishing Switzerland 2015. This paper provides an overview of the progress made in a study of the coherent structures of feedback loops found in under-expanded free-jets. In order to gain a better understanding of the topology and dynamics of these structures the proper-orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques will be applied to high resolution numerical datasets.We consider a purely convergent under-expanded free jet with nozzle pressure ratios NPR = {2.2, 2.6} and a nozzle lip thickness tn/d = 1/3 where d = 15mm is the nozzle diameter. The analysis has shown that DMD is more capable than POD in extracting the structure of ins..