Journal
JOURNAL OF FLUID MECHANICS
Volume 828, Issue -, Pages 812-836Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.1017/jfm.2017.489
Keywords
absolute/convective instability; jets; turbulent flows
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Funding
- AFOSR [FA9550-15-1-0261]
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The stability of low-speed jets in cross-flow (JICF) is studied using tri-global linear stability analysis (GLSA). Simulations are performed at a Reynolds number of 2000, based on the jet exit diameter and the average velocity. A time stepper method is used in conjunction with the implicitly restarted Arnoldi iteration method. GLSA results are shown to capture the complex upstream shear-layer instabilities. The Strouhal numbers from GLSA match upstream shear-layer vertical velocity spectra and dynamic mode decomposition from simulation (Iyer & Mahesh, J. Fluid Mech., vol. 790, 2016, pp. 275-307) and experiment (Megerian et al., J. Fluid Mech., vol. 593, 2007, pp. 93-129). Additionally, the GLSA results are shown to be consistent with the transition from absolute to convective instability that the upstream shear layer of JICFs undergoes between R = 2 to R = 4 observed by Megerian et al. (J. Fluid Mech., vol. 593, 2007, pp. 93-129), where R = (v) over bar (jet)/u(infinity) is the jet to cross-flow velocity ratio. The upstream shear-layer instability is shown to dominate when R = 2, whereas downstream shear-layer instabilities are shown to dominate when R = 4.
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