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Now showing items 1-10 of 11

#### Multiple instability of layered stratifed plane Couette flow

(Cambridge University PressJournal of Fluid Mechanics, 2017-02-25)

We present the linear stability properties and nonlinear evolution of two-dimensional plane Couette flow for a statically stable Boussinesq three-layer fluid of total depth 2$h$ between two horizontal plates driven at ...

#### Nonlinear evolution of linear optimal perturbations of strongly stratified shear layers

(Cambridge University PressJournal of Fluid Mechanics, 2017-08-25)

The Miles-Howard theorem states that a necessary condition for normal-mode instability in parallel, inviscid, steady stratified shear flows is that the minimum gradient Richardson number, $Ri_{g,min}$, is less than 1/4 ...

#### Nonlinear effects in buoyancy-driven variable-density turbulence

(Cambridge University PressJournal of Fluid Mechanics, 2017-01-01)

We consider the time dependence of a hierarchy of scaled L²ᵐ-norms D_m,ω and D_m,θ of the vorticity ω =∇ x u and the density gradient ∇θ, where θ = log.(ρ*/ ρ*₀), in a buoyancy-driven turbulent flow as simulated by Livescu ...

#### Efficiency of turbulent mixing in the abyssal ocean circulation

(American Geophysical UnionGeophysical Research Letters, 2017-07-17)

Turbulent mixing produced by breaking of internal waves plays an important role in setting the patterns of downwelling and upwelling of deep dense waters and thereby helps sustain the global deep ocean overturning circulation. ...

#### Self-similar mixing in stratified plane Couette flow for varying Prandtl number

(Cambridge University PressJournal of Fluid Mechanics, 2017-06-10)

We investigate fully developed turbulence in stratified plane Couette flows using direct numerical simulations similar to those reported by Deusebio et al. (J. Fluid Mech., vol. 781, 2015, pp. 298-329) expanding the range ...

#### Diapycnal mixing in layered stratified plane Couette flow quantified in a tracer-based coordinate

(Cambridge University PressJournal of Fluid Mechanics, 2017-07)

The mixing properties of statically stable density interfaces subject to imposed vertical shear are studied using direct numerical simulations of stratified plane Couette flow. The simulations are designed to investigate ...

#### Role of overturns in optimal mixing in stratified mixing layers

(Cambridge University PressJournal of Fluid Mechanics, 2017-09-10)

Turbulent mixing plays a major role in enabling the large scale ocean circulation. The accuracy of mixing rates estimated from observations
depends on our understanding of basic fluid mechanical processes underlying the ...

#### Adjoint-based optimization of displacement ventilation flow

(ElsevierBuilding and Environment, 2017-11-01)

We demonstrate the use of the ‘Direct-Adjoint-Looping method’ for the identification of optimal buoyancy-driven ventilation flows governed by Boussinesq equations. We use the incompressible Reynolds-averaged Navier-Stokes ...

#### Coherent structures in interacting vortex rings

(American Physical SocietyPhysical Review Fluids, 2017-02-21)

We investigate experimentally the nonlinear structures that develop from interacting vortex rings induced by a sinusoidally oscillating ellipsoidal disk in fluid at rest. We vary the scaled amplitude or Keulegan-Carpenter ...

#### Irreversible mixing by unstable periodic orbits in buoyancy dominated stratified turbulence

(Cambridge University PressJournal of Fluid Mechanics, 2017-10-26)

We consider turbulence driven by a large-scale horizontal shear in Kolmogorov flow
(i.e. with sinusoidal body forcing) and a background linear stable strati cation with buoyancy frequency $N^2_B$ imposed in the third, ...