Diffusion of Matter from a Continuous Point Source in Uniform Mean Shear Flows : 1st Report, Characteristics of the Mean Concentration Field

Abstract

The turbulent diffusion process has been examined experimentally in the case of a continuous point source in turbulent water flows with three different uniform mean shear rates. Shear-flow generators used were non-uniformly spaced rods, and the diffusing matter was a dye solution. The present study mainly deals with the characteristics of the mean concentration field. It is revealed that the horizontal and vertical profiles of the mean concentration are nearly similar, and vertical profiles in particular are skewed to the side with a smaller flow velocity by the shear effect. A diffusion model for a continuous point source by Okubo & Karweit (1969) is investigated and compared with the experimental results. The effect of shear rate on the spread of matter is discussed on the basis of this model.