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THE STRUCTURE OF PASSIVE SCALAR PLUMES IN TURBULENT BOUNDARY LAYERS

John P. Crimaldi
Department of Civil and Environmental Engineering, University of Colorado 428 UCB, Boulder, CO 80304-0428 USA

Jeffrey R. Koseff
Department of Civil and Environmental Engineering Stanford University Stanford, California, USA 94305-4020

Аннотация

We present results of an experimental investigation of the temporal and spatial structure of a scalar plume developing within a turbulent boundary layer over a smooth bed. The source of the scalar plume is located flush with the bed, and the vertical momentum associated with the scalar release is extremely small. The source design is intended to simulate a diffusive-type scalar release. Planar laser-induced fluorescence (PLIF) and single-point laser-induced fluorescence (LIF) techniques were used to capture the spatial and temporal structure of the plume at resolutions of 150 μm and 2000 Hz, respectively. We present data that describes the characteristics of the mean and fluctuating scalar fields, including the scalar intermittency and the probability density function (pdf) of scalar differences. The results show a strong vertical variation in the plume structure typical of boundary layer flows.