Acoustic Signature of a Supersonic Jet Emanating from a Rectangular C-D Nozzle

Paper in proceeding, 2016

We live in a world with ever increasing air traffic and the demand for fuel efficient low noise emitting aircraft is high. The use of blended wing bodies (BWB) has gained interests within the aerospace industry due to its potential for reduced fuel consumption. These type of aircraft are generally equipped with rectangular nozzles. The drawback of such nozzles is increased instability of the emanating jet which increases the risk of higher noise radiation. Understanding the instability patterns and the underlying flow physics is therefore the key to improved stability and reduced noise. In the presented paper, an LES/CAA approach is utilized to predict the flow dynamics and the radiated noise from a rectangular nozzle. The nozzle is operated at underexpanded conditions. The simulations are compared with experiments and are used as a complement to the experimental data for improved understanding of the flow physics. The supersonic jet is found to exhibit an intense flapping motion followed by a large jet spreading in the minor-axis plane. In general, the prediction of the most amplified frequency and higher harmonics observed in the near-field and far-field spectra is in agreement with the experiment. Two types of flow events associated with the generation of high amplitude acoustic waves are detected. These events are identified as vortex-collision and shock-leakage through the shear layer.