Similarity criterion in physical simulation of rainfall and sheet flow

At present, rainfall runoff simulations using Froude (Fr) criterion give rise to the large difference results between simulated and field situations. Using theoretic analytic method, similarity criterion in physical simulation of rainfall runoff was determined through comparing the magnitude of each applied force in the course of the rainfall runoff. Rationality and accuracy of the similarity criterion were validated with the experimental data. Suspended similar conditions were carried out depending on the flow velocity distribution of the thin layer of uniform flow. It was concluded that Re criterion was leading when the diameters of raindrops were less than 1.0 mm, otherwise there could be no similarity criterion. Rainfall similarity was determined by sheet flow similar leading criteria, which was the Weber (We) criteria and the scale of the geometric should be greater than 10, taking into account the variable amplitude of the normal raindrops diameters were 0.1-3.5 mm. The research can provide a reference for experimental design of rainfall and sheet flow simulation.