The dynamic response to a westerly wind burst which occurred during the Couple Ocean Atmosphere Response Experiment in the warm pool of the equatorial Pacific Ocean is described using velocity, hydrography, and microstructure measurements. Turbulent fluxes distributed momentum input from the wind over a near-surface layer of variable thickness. Coriolis...
A westerly wind burst observed in the warm pool of the western equatorial Pacific Ocean cooled the ocean's surface layer by about 0.8°C. Turbulent entrainment at the base of this layer caused cooling but also heating due to the reversal of the vertical temperature gradient during rain events. Consequently, the...
The role of stratified shear instability in maintaining the deep cycle of
turbulence immediately below the equatorial mixed layer is examined by means of
linear stability analysis. The Taylor-Goldstein equation is solved numerically, using
observed currents and stratification from the Tropical Instability Wave Experiment
(TIWE). Multiple unstable modes are found,...
Direct numerical simulations of turbulence resulting from Kelvin{Helmholtz instability
in stratified shear flow are used to examine the geometry of the dissipation
range in a variety of flow regimes. As the buoyancy and shear Reynolds numbers that
quantify the degree of isotropy in the dissipation range increase, alignment statistics
evolve...
Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz instability in stably
stratified shear flow are used to study sources of anisotropy in various spectral ranges. The set of
simulations includes various values of the initial Richardson and Reynolds numbers, as well as
Prandtl numbers ranging from 1 to 7. We...
Turbulence resulting from Kelvin–Helmholtz instability in layers of localized stratification and shear is studied by means of direct numerical simulation. Our objective is to present a comprehensive description of the turbulence evolution in terms of simple, conceptual pictures of shear–buoyancy interaction that have been developed previously based on assumptions of...
The growth of secondary vortices on the braids separating Kelvin–Helmholtz billows is investigated via numerical simulations. The similarity theory of Corcos & Sherman (1976) is extended to include mixing processes with Prandtl number greater than unity, and is shown to provide a useful description of the physics of the braid...
The envelope function for Kelvin–Helmholtz billows growing from a point disturbance is derived on the basis of linear perturbation theory. The result describes an elliptical patch of billows that expands linearly in time as the billows grow. An analytical model of the dispersion relation is used to derive quantitative expressions...
A sequence of direct simulations is used to study mechanisms for the growth of secondary
circulations and turbulence in stratified shear flows. Five cases are examined, of which four deliver
Holmboe waves as the primary instability and the fifth generates Kelvin-Helmholtz billows.
Secondary circulations range in strength from weak, laminar...
When a stably stratified density interface is embedded in a region of strong velocity
shear, hydrodynamic instabilities result. Here we generalize the stratified shear layer
to allow an offset between the centre of the shear layer and the density interface. By
including this asymmetry, and keeping the density interface thin...