Structure of Turbulent Convection over Non-uniform Horizontal Surfaces

湍流流动的实验研究将在广泛的流体层中进行，这些流体层模拟了大气边界层的许多基本方面。这些层中的湍流运动是由下表面的浮力加热引起的，下表面通常是水平的。实验的目的是了解湍流是如何从特征连贯结构（如热流和羽流）中组织起来的，并确定表面几何形状和热模式的细节如何影响这些结构和宏观平均现象（如热输送、湿度输送和污染物输送）。为此，实验将在三种类型的表面上进行：光滑，粗糙和非均匀，主要强调后者。不均匀的表面具有与层深相当的尺度上的加热或高程模式。高分辨率粒子图像测速仪技术将用于测量流动中的瞬时速度矢量场，激光诱导荧光技术将用于测量瞬时温度场。将开发新的技术来测量温度、浓度和速度矢量场的标量场的三维结构。通过直接检测和空间相关技术、随机估计和适当的正交分解等统计方法，可以推导出运动模式。将测量场的基本性质，如湍流动能的分布、各矩的输运和耗散。在均匀表面的情况下，关于垂直方向的统计轴对称将允许完全确定两点空间相关函数，由此可以精确测量粘性耗散。粗糙表面研究将集中于正弦表面形状，而非均匀研究将考虑各种非均匀加热模式，如阶跃函数、单片正方形和棋盘。所获得的信息将有助于测试和开发大涡模拟。

Adrian/Abstract Experimental studies of turbulent fluid flow will be conducted in wide fluid layers that model many fundamental aspects of the atmospheric boundary layer. Turbulent motions in these layers are caused by buoyant heating of the lower surface, which is typically horizontal. The purposes of the experiments are to understand how turbulent flows are organized from characteristic coherent structures such as thermals and plumes,and to determine how details of the surface geometry and heat patterns affect these structures and the macroscopic mean phenomena such as heat transport, humidity transport and transport of pollutants. To this end experiments will be conducted over three types of surfaces: smooth, rough and inhomogeneous, with primary emphasis on the latter. The inhomogeneous surface have patterns of heating or elevation that are on a scale comparable to the layer depth. High resolution particle image velocimeter techniques will be used to measure instantaneous velocity vector field in flow, and laser induced fluorescence will be used to measure instantaneous temperature fields. New techniques will be developed to measure the three dimensional structure of the scalar fields of temperature and concentration and velocity vector fields. From the measurements patterns of motion will be educed by direct inspection and by statistical methods such as spatial correlation techniques, stochastic estimation and proper orthogonal decomposition. Basic properties of the fields such as distribution of turbulent kinetic energy, transport of various moments and dissipation will be measured. In the case of homogeneous surfaces, the statistical axisymmetry about the vertical will allow complete determination of the two-point spatial correlation function, from which accurate measurement of the viscous dissipation will be possible. The rough surface study will concentrate on sinusoidal surface shapes, while the inhomogeneous study will co nsider variety of inhomogeneous heating patterns such as a step function, a monolithic square, and a checkerboard. The information obtained will be useful in testing and developing large eddy simulations.