Noise Generation in the Near-Nozzle Region of a Chevron Nozzle Jet Flow

This paper reports on the simulation of the near-nozzle region of a moderate Reynolds number cold jet flow exhausting from a chevron nozzle. The chevron nozzle considered in this study is the SMC001 nozzle experimentally studied by the researchers at the NASA Glenn Research Center. This nozzle design contains six symmetric chevrons that have a five-degree penetration angle. The flow inside the chevron nozzle and the free jet flow outside are computed simultaneously by a high-order accurate, multi-block, large eddy simulation (LES) code with overset grid capability. The total number of grid points at which the governing equations are solved is about 100 million. The main emphasis of the simulation is to capture the enhanced shear layer mixing due to the chevrons and the consequent noise generation that occurs in the mixing layers of the jet within the first few diameters downstream of the nozzle exit. Details of the computational methodology are presented together with an analysis of the simulation results. The simulation data are compared with available experimental flow field measurements for the same nozzle geometry. A comparison of the noise spectrum in the sideline direction with experimental data is also carried out. Overall, the simulation results are very encouraging and demonstrate the feasibility of chevron nozzle jet computations using our simulation methodology.