On Diffusion from an Instantaneous Point Source in a Neutrally Stratified Turbulent Boundary Layer with a Laser Light Scattering Probe

摘要

The behavior of an instantaneous point source, as it disperses in a thick, neutrally stratified, turbulent shear layer, has been examined by a laser light-scattering technique in the Meteorological Wind Tunnel. An aerosol-filled gas bubble was released in a column of water to subsequently rise and burst at the floor of the wind tunnel. This pseudo-instantaneous gas volume dispersed in the turbulent shear layer. Time dependent concentrations at a point were monitored by measuring the scattered light from a coherent light source by a photomultiplier-fiber optics probe. Data consisted of a series of concentration realizations downstream from the ground level source. The distribution of concentration was described by selecting coefficients empirically in a Gram-Charlier series. Puff dispersion characteristics were compared with prediction of the Lagrangian similarity diffusion theory. (Author Modified Abstract)