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Published May 2016 | public
Journal Article

Large-Eddy Simulation of Supersonic Round Jets: Effects of Reynolds and Mach Numbers

Abstract

Large-eddy simulations of supersonic turbulent jets are performed for Reynolds numbers of Re < 10,000 for the purpose of understanding the effects of Reynolds numbers and the Mach number M. The subgrid terms in large-eddy simulations are modeled using a combination of the dynamic Smagorinsky ("General Circulation Experiments with the Primitive Equations. Part I, Basic Experiments," Monthly Weather Review, Vol. 54, No. 1, 1963, pp. 99–164) and Yoshizawa ("Statistical Theory for Compressible Turbulent Shear Flows, with the Application to Subgrid Modelling," Physics of Fluids, Vol. 54, No. 1, 1986, pp. 2152–2164) models. Simulations are performed for supersonic jets having Reynolds numbers of 1500, 3700, and 7900, and Mach numbers of 1.4 and 2.1. Two of the simulations are validated with experimental data. The Reynolds number value is observed to play a role in the transition to turbulence but, once transition is achieved, it has a subdued effect above a threshold value; that is, as seen experimentally for supersonic flows, a similarity is found here. This similarity occurs for Reynolds number values that are relatively small compared to those typical of the fully turbulent regime. The turbulent structures in the transition region are more coherent, and the potential core is longer when the Mach number is larger, which leads to a slower downstream velocity decay. The root-mean-square velocities are biased in the axial direction, as expected. In the fully turbulent regions, the computed Reynolds stress is higher for a larger-Mach-number jet. Peak pressure fluctuations occur at about half a jet diameter, radially away from the centerline of the jet, and this location is independent of both the Reynolds number and Mach number values. The pressure–velocity correlations and the turbulent kinetic energy profiles are investigated along the centerline and radial directions, and it is found that the peak turbulent kinetic energy occurs at the same location as the maximum pressure fluctuations.

Additional Information

© 2015 by the American Institute of Aeronautics and Astronautics. Received 11 June 2015; revision received 20 November 2015; accepted for publication 24 November 2015; published online 20 January 2016. This study was conducted at the Jet Propulsion Laboratory of the California Institute of Technology and was sponsored by the NASA Science Mission Directorate Lunar Advanced Science and Exploration Research (LASER) program. Kaushik Balakrishnan is acknowledged for his contributions to this study. The simulations were carried out at the NASA Advanced Supercomputing Division at NASA Ames Research Center. The author is very grateful to Wai-Sun Don (Brown University), who provided the baseline parallelization framework.

Additional details

Created:
August 20, 2023
Modified:
October 17, 2023