Buoyant Water Research Articles

The Dynamics of Oceanic Fronts. Part II: Shelf Water Structure Due to Freshwater Discharge

Abstract In Part I of this series, a framework was introduced for the study of oceanic frontal dynamics. The dynamics was studied by posing an initial value problem, starting with a near-surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density. An essential aspect of the framework was the identification of the proper length scales: an inertial length scale L0, a buoyancy length scale h0 and a diffusive length scale hv. In Part I, the horizontal and vertical dimensions were scaled by L0 and h0, respectively; and two dimensionless parameters were formed, viz., Ro = L0/h0 and E = (hv/h0)2. It was shown in Part I that under this scaling, the normalized equations depended on E only for Ro sufficiently large. The solution for E small, i.e., for the almost inviscid case, was given in Part I; and the equilibrium state was discussed in a frame of reference in which the front was stationary. In this paper, we present the solution for large E. It will b...

The Dynamics of Oceanic Fronts. Part I: The Gulf Stream

The establishment and maintenance of the mean hydrographic properties of large scale density fronts in the upper ocean is considered. The dynamics is studied by posing an initial value problem starting with a near surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density. The full time dependent diffusion and Navier-Stokes equations for a constant Coriolis parameter are used in this study. Scaling analysis reveals three independent length scales of the problem, namely a radius of deformation or inertial length scale, Lo, a buoyance length scale, ho, and a diffusive length scale, hv. Two basic dimensionless parameters are then formed from these length scales, the thermal (or more precisely, the densimetric) Rossby number, Ro = Lo/ho and the Ekman number, E = hv/ho. The governing equations are then suitably scaled and the resulting normalized equations are shown to depend on E alone for problems of oceanic interest. Under this scaling, the solutions are similar for all Ro. It is also shown that 1/Ro is a measure of the frontal slope. The governing equations are solved numerically and the scaling analysis is confirmed. The solution indicates that an equilibrium state is established. The front can then be rendered stationary by a barotropic current from a larger scale along-front pressure gradient. In that quasisteady state, and for small values of E, the main thermocline and the inclined isopycnics forming the front have evolved, together with the along-front jet. Conservation of potential vorticity is also obtained in the light water pool. The surface jet exhibits anticyclonic shear in the light water pool and cyclonic shear across the front.

Heated Water Jet in Coflowing Turbulent Stream

The effects of ambient turbulence on temperature and salinity distributions of heated water and neutrally buoyant salt water jets were studied for a wide range of densimetric jet Froude numbers, jet discharge velocities, and ambient turbulence levels in a 4-ft wide channel. Estimates of vertical and lateral diffusivity coefficients for heat and for salt were obtained from salinity and temperature distributions taken at several stations downstream of the injection point. Readily usable correlations are presented for plume center-line temperature, plume width, and trajectory.

The interaction of liquid droplets with a grain boundary in large accelerational fields

Abstract A buoyant water droplet was migrated through a 15° twist boundary in a crystal of KCl in a large accelerational field. On passing through and away from the twist boundary plane, a columnar 15° tilt boundary linking the droplet and the twist boundary plane was generated. The surface tension of this columnar boundary exerted a force, pulling the droplet back towards the twist boundary plane. The accelerational field was adjusted so as to produce a buoyant force on the droplet which just balanced the backward pull of the columnar tilt boundary. The balancing accelerational field indicated that the surface energy of a 15° tilt boundary in KCl is 75 ± 20 ergs/cm2

A Scaled-Model Experiment of Wave Propagation in a Randomly Inhomogeneous Medium—II

When a tank of water is heated from below, the turbulent mixing of warmer, more buoyant water produces thermal inhomogeneities and related variations in the index of refraction. The acoustic fluctuations are determined experimentally as a function of the microstructure parameters. The significant parameters of the microstructure are separately measured with thermistors; provision is made to determine the temperature fluctuations at a single point or the correlation of the fluctuations at two points. The relations between the acoustic and the microstructure fluctuations are then determined, and compared with the theory of Mintzer. There is the interesting possibility of determining the parameters of the temperature microstructure by means of acoustic waves. (Supported by the Office of Naval Research.)