• Letter

Criterion for the linear convective to absolute instability transition of a jet in crossflow: The countercurrent viscous and round mixing-layer analogy

Davi B. de Souza, Rômulo B. Freitas, and Leonardo S. de B. Alves
Phys. Rev. Fluids 6, L041901 – Published 15 April 2021

Abstract

The jet in crossflow, or a transverse jet, eventually undergoes a linear transition from convectively to absolutely/globally unstable as the crossflow to jet velocity ratio increases. This flow field, however, has an extremely complex dynamics. Hence, determining this transition location is not a trivial task. It has long been known that this transition is associated with the upstream shear layer connected to the near field Kelvin-Helmholtz vortex ring, but it was only recently that the most unstable global mode and wave maker were located there as well. These findings led to the realization that an inviscid and planar linear stability analysis of the local velocity profile extracted from the jet in the crossflow upstream shear layer was strongly correlated with its transition to absolute/global instability. It is shown in this paper that such an analysis can be turned into an accurate predictive tool with the use of a viscous (instead of inviscid) and round (instead of planar) mixing layer. In other words, replacing an inviscid analysis of a planar mixing layer with counterflow by a viscous analysis of a round coaxial jet with outer nozzle suction leads to an accurate prediction of the jet in crossflow convective to an absolute instability transition.

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  • Received 17 December 2020
  • Accepted 23 March 2021

DOI:https://doi.org/10.1103/PhysRevFluids.6.L041901

©2021 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Davi B. de Souza, Rômulo B. Freitas*, and Leonardo S. de B. Alves

  • PGMEC, UFF, Rua Passo da Pátria 156, Bloco E, Sala 211, Niterói, Rio de Janeiro 24210-240, Brazil

  • *Also at CEFET/RJ, Estrada de Adrianópolis, 1.317, Santa Rita, Nova Iguaçu, RJ 26041-271, Brazil.
  • lsbalves@id.uff.br

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Vol. 6, Iss. 4 — April 2021

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