Instability and turbulence in sheared, salt-fingering favorable stratification are studied
using three-dimensional direct numerical simulations (DNS). Salt-fingering favorable
stratification is gravitationally stable, because the unstable vertical gradient of salinity
is stabilized by temperature (warm, salty over cool, fresh water-masses). Salt-fingering
instability can occur at the interface of these different water-masses....
Vertical transports of plankton, momentum, heat, and turbulence are modeled. A novel integration of high resolution turbulence and biophysical modeling is used to show the influence of a Kelvin-Helmholtz instability on the vertical migration of simple gyrotactic organisms. A viscous limit on mixing driven by shear turbulence is proposed. Large...
A small eddy viscosity or mass diffusivity that varies with height has been found to have unexpected effects on the Kelvin-Helmholtz (KH) instability of a stably stratified shear layer near the neutral stability boundary. In particular, varying viscosity can increase the growth rate of the instability in contrast to the...
Thermohaline interleaving is an important mechanism for laterally fluxing salt, heat, and nutrients between oceanic water masses. Interleaving is driven by a release of potential energy resulting from the vastly differing diffusivities of heat and salt in seawater. The flows are composed of stacked intrusions that flux more buoyant and...
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...
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...
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...
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...
A field study was conducted to determine the applicability of multivariate
geostatistical methods to the problem of estimating and simulating pesticide
concentrations in groundwater from measured concentrations of nitrate and pesticide,
when pesticide is undersampled. Prior to this study, no published attempt had been made
to apply multivariate geostatistics to...
The dependence of mixing efficiency on time-varying forcing is studied by direct numerical simulation
(DNS) of Kelvin–Helmholtz (KH) instability. Time-dependent forcing fields are designed to reproduce a
wavelike oscillation by solving the equations of motion in a tilted coordinate frame and allowing the tilt angle
to vary in time. Mixing...