Bill Smyth

Associate Professor

(541) 737-3029







Fluid turbulence represents a major unsolved problem in applied physics, as well as an essential component governing the behavior of geophysical fluid systems. Efforts to understand and parameterize turbulent mixing have been a research focus over the past several decades, and continue to be essential to improved understanding and prediction of the evolution of Earth's atmosphere and oceans.

The past decade has brought tremendous insights into the physics of turbulence, due largely to direct numerical simulations (DNS). This new understanding applies almost entirely to the simplest idealization, i.e. stationary, homogeneous, isotropic turbulence. In nature, turbulence never conforms to this simple picture. In particular, geophysical turbulence is almost always affected by ambient shear, density stratification and planetary rotation, which complicate the physics greatly. The turbulence modeling program at COAS aims to extend state-of-the-art theories of turbulence to small-scale geophysical flows by accounting for these effects.


Turbulence in shear-driven overturns

A recent focus has been DNS of turbulence resulting from breaking Kelvin-Helmholtz billows, wavelike vortical structures that arise due to the dynamical instability of localized layers of shear and stratification. This scenario provides a useful model for many of the turbulent events that are observed in the Earth's atmosphere and oceans. The following links lead to summaries of developments in this area.


Turbulent patches and banded clouds

Turbulence in Holmboe Waves

Overview / mixing efficiency

Length scales


In search of "q"


Catastrophic breakdown of barotropic vortices

One-dimensional vortices are an essential feature of turbulence on the smallest scales of motion, but they can also describe macroscale structures such as hurricanes, tornadoes and waterspouts. When such a vortex evolves in a rotating, stratified environment, it exhibits one of two behaviors: scale-selective instability, which leads to the formation of three-dimensional vortex lenses, and ultraviolet catastrophe, which leads to the rapid development of turbulence and subsequent breakdown of the vortex.  Click here for a summary of recent research.


Other materials of interest:

A turbulence primer (PDF, 1.4Mb)

Download recent publications

Ocean Turbulence and Global Climate

Ocean Art

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This research is supported by the National Science Foundation


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