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.
