Laboratory Experiments on Nonlinear Waves and Turbulence

实验室实验是在三个流体系统上进行的，它们显示了在地球和行星大气动力学中重要的过程：(1)由差动旋转的盖子驱动的旋转圆柱体中的非线性波和湍流。在这个系统中的不稳定性导致旋转的波由于有尖锐的拐角而偏离平滑的圆形或椭圆形。这些所谓的“多边形”波在外观上类似于在飓风眼壁和土星极地大气中观察到的波。(2)旋转水跃中的失稳和波浪形成。旋转出流层中的圆形水力跃迁是形成多边形波的另一种机制。(3)湍流旋转对流中进动平均流的结构和力学。直接测量涡应力和平均流剖面将解释旋转湍流对流中平均流的产生机制。这些实验提供了类似于大气中的非线性流动的数据，这些数据很难通过任何其他手段获得。此外，它们还提供了在地球物理流动的大涡模拟(LES)中评估小尺度湍流参数化所需的信息。涉及与大气中的约束类似的受控实验室实验(特别是旋转和层化)提供了一个宝贵的试验场。这些和类似的实验室实验被用在研究生和本科生的课堂上，以演示与大气科学相关的基本流体过程。

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.