Effects Of Turbulent Transport Research Articles

The Circulation Dynamics and Thermodynamics of Upper Ocean Density Fronts

This paper extends a previous hydrodynamic circulation model of established, persistent upper ocean density fronts by including a thermodynamic or buoyancy equation in the integral treatment. An analysis is also conducted of the variables related to the kinetic and potential energy budgets in the frontal zone. A comparison of the new results with previous ones shows satisfactory agreement. The new model is used to explore three frontal types of widely different scale or rotation effect, a river plume front, a Sargasso Sea front and the Gulf Stream front. As the scale increases, the influence of rotation increases and the effect of interfacial turbulent transport diminishes. Also, with increasing scale the strength of the downstream (alongfront) flow increases while the cross-stream flow diminishes, but always shows a two-sided convergence near the surface front. The kinetic energy dissipation decreases rapidly with dissipation times of resident kinetic energy increasing from ten minutes for the river plume front to a week for the Gulf Stream front. The model results are examined in an attempt to answer three questions about the circulation dynamics. They indicate that the direction of turbulent mass entrainment is always downward, that fronts always spread, even if slowly, relative to the ambient fluid, and that the cross-stream flow near the surface front always shows a two-sided convergence.

An Integral Hydrodynamic Model of Upper Ocean Frontal Dynamics: Part II. Physical Characteristics and Comparison with Observations

Abstract The physical characteristics of a model of an upper ocean density front are examined and compared to observations. The model was developed and analyzed in a companion paper. It applies to the mean circulation and hydrography of established, persistent fronts. The results for a case where turbulent transport and earth rotational effects are both important are examined in detail. The circulation then contains a jet for the velocity parallel to the front including a cyclonic shear zone but with speeds that are below geostrophic values. The circulation normal to the front shows strong two-sided convergence and sinking near the surface front. The question of upward versus downward mass entrainment is examined in terms of its impact on the model circulation. Five frontal cases are examined and compared to field observations. These cover a wide range of frontal scales from a river plume front to the Gulf Stream front. The river plume front nearly corresponds to a limiting case for the model where rotati...

A Simple Statistical Treatment of Highly Turbulent Couette Flow

Abstract From the integral conditions for momentum and kinetic energy balance in the state of fully developed turbulence, it is found possible to estimate the bulk statistical properties of highly turbulent Couette flow as functions of the Reynolds number. The average boundary shear, boundary layer thickness, and average momentum transport through the “constant flux” layer are determined to within the value of a single non-dimensional constant. The conclusions of this analysis are in quantitative agreement with laboratory measurements and are consistent with empirical formulas for the Reynolds stress over smooth surfaces. The significance of the results is discussed with specific reference to the problem of “parameterizing” the statistical effects of turbulent momentum transport in terms of the large-scale average motion of the atmosphere.