Predicting vortex merging and ensuing turbulence characteristics in shear layers from initial conditions

Anirban Guha (Lead / Corresponding author), Mona Rahmani

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Abstract

Unstable shear layers in environmental and industrial flows roll up into a series of vortices, which often form complex nonlinear merging patterns such as pairs and triplets. These patterns crucially determine the subsequent turbulence, mixing and scalar transport. We show that the late-time, highly nonlinear merging patterns are predictable from the linearized initial state. The initial asymmetry between consecutive wavelengths of the vertical velocity field provides an effective measure of the strength and pattern of vortex merging. The predictions of this measure are substantiated using direct numerical simulations. We also show that this measure has significant implications in determining the route to turbulence and the ensuing turbulence characteristics.
Original languageEnglish
Number of pages12
JournalJournal of Fluid Mechanics
Early online date17 Sep 2019
DOIs
Publication statusPublished - 10 Nov 2019

Keywords

  • transition to turbulence
  • shear layer turbulence
  • vortex interactions

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