Laboratory Experiments on Nonlinear Waves and Turbulence

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Laboratory experiments are carried out on three fluid systems that manifest processes important in the dynamics of terrestrial and planetary atmospheres: (1) Nonlinear waves and turbulence in a rotating cylinder driven by a differentially rotating lid. Instabilities in this system lead to rotating waves that deviate from smooth circular or elliptical shape by having sharp corners. These so-called "polygonal" waves are similar in appearance to waves observed in hurricane eyewalls and in the polar atmosphere of Saturn. (2) Instability and wave formation in a rotating hydraulic jump. A circular hydraulic jump in a rotating outflow layer is an alternative mechanism for the formation of polygonal waves. (3) The structure and mechanics of precessing mean flows in turbulent rotating convection. Direct measurements of eddy stresses and mean flow profiles will explain the mechanism of mean-flow generation in rotating turbulent convection. These experiments provide data on nonlinear flows analogous to those in the atmosphere that are difficult to obtain by any other means. Moreover, they give the information needed to evaluate small-scale turbulence parameterization in large-eddy simulations (LES) of geophysical flows. Controlled laboratory experiments that involve constraints similar to those in the atmosphere (particularly rotation and stratification) provide a valuable testing ground. These and similar laboratory experiments are used in graduate and undergraduate classes to demonstrate fundamental fluid processes of relevance to atmospheric science.