Tony Maxworthy - US grants

Investigators at the University of Southern California will undertake research to model and investigate some of the important dynamical processes that have been identified in the Arctic Ocean and adjacent Seas. The Arctic Ocean and its adjacent seas play an important role in global warming, and it is important to understand its dynamical behavior on many space and time scales. At several locations during the winter, major sources of dense cold seawater are formed and sink. Much of this water reaches great depths and eventually spreads through the world's ocean basins. This thermo- haline circulation is a major factor in understanding the long-term evolution of the coupled atmosphere-ocean system. This work will examine some aspects of this problem. Primarily, the mechanisms whereby the motion of the dense water that is formed by intense cooling and/or freezing is controlled by the environment in which it is created. Among the issues of interest are: a) The origin and dynamics of small and meso-scale eddy structures that have been observed repeatedly by satellite (IR) images and reported by field investigators at different Arctic locations. b) The formation of a halocline between the upper mixed layer and the underlaying Atlantic water, which tends to shield the ice cover from an upward heat flux. c) The upwelling and/or downwelling processes that have been observed in the marginal ice zones. d) Interaction between the shelf and the basin waters. To accomplish this work, both laboratory experiments and numerical calculations will be made with well defined objectives. A wide range of generic problems will be tackled starting from the simplest convection experiment with a non-uniform heat flux to the most complex in which virtually all of the controlling parameters are incorporated. In this way individual and combined effects of these various inputs can be studied.

ABSTRACT Proposal Number: CTS-9523291 PI: Maxworthy This is a comprehensive and carefully integrated computational and experimental investigation of the evolution of swirling jets. These flows are of practical significance in a broad range of applications. In spite of this practical significance, the mechanisms that govern their spatio-temporal dynamics of these flows are poorly understood. Swirling jets are subjected to both shear and centrifugal instabilities and therefore exhibit a rich and varied set of disturbance modes. The generation, existence, and interaction of these mechanisms has not been investigated in any detail. It is expected that the identification, quantification, and eventual control of the governing structures by means of vortex dynamics and direct Navier-Stokes simulations, as well as experimental DPIV measurements will significantly advance the state of the art in a variety of propulsion, combustion and mixing applications.

0080069/Smethie

This project consists of a study of the way in which dense water is
formed on a shelf and then descends to depth when the shelf-water is
subject to a negative surface buoyancy flux. The intent is to model
dense water formation on continental shelves with the Weddell Sea quoted
as the main motivation. The approach is to perform laboratory
experiments in a rotating tank with a simplified shelf-slope geometry.
The experiments are distinguished from earlier experiments by the use of
a distributed surface buoyancy flux, by a novel approach to trying to
quantify the viscous flow draining fluid from the down-slope gravity
currents, and by the inclusion of canyons and ridges on the slope
topography.