Characteristics of Shallow Rain-Impacted Flow over Smooth Bed

Abstract

An understanding of the effect of rainfall on the characteristics of shallow flow is needed for the proper modeling of the physical processes related to erosion and sedimentation. In this study, the turbulence characteristics of shallow rain-impacted flow over a smooth bed were investigated using a fiber-optic laser Doppler velocimeter and a specially designed artificial raindrop simulator. An empirical formula was derived to predict the variation of momentum correction factor β with the parameters related to the flow and the rainfall characteristics. Statistical correlations were developed successfully to predict the distributions of both the longitudinal and the vertical turbulence intensities for rainfalls with different intensities and raindrop diameters. The statistical characteristics of the Reynolds stress under different rainfall conditions also were analyzed. Analysis of the energy spectrum of the longitudinal velocity component indicated that the energy for the large-scale eddies (low frequencies) was increased significantly because of the mixing effect of the raindrop impact for the region near the water surface.