Study of submountain river flow patterns constrained by a combined dam

Abstract

Abstract Great attention around the world is paid to the design and construction of riverbank protection and channel control structures on submountain section of rivers. High slopes (i=0,001÷0,004 and higher), flow kinetics and ability to transport large amount of sediments are the features of submountain section of rivers. Most of the research in this sphere has been conducted on the study of patterns of flow constrained by transverse structures in valley parts of rivers. The main goal of this work is to establish the physical picture of flow around a combined dam in submountian river, the through-flow part of which is made of tetrahedrons, as well as to develop a design method for flow velocity field. Formations of two regimes have been established experimentally, i.e. “calm” at ia<icr and “critical” at ia≥icr. These regimes are mainly affected by flow contraction degree na, and Froude number Fr. The presence of the following zones was established: core, intensive turbulent mixing and backflow zones, as well as the affinity of velocity fields in the zone of mixing by Shlihting-Abramovich. Prandtl has realized the task for “calm” regime with the use of integral relationship expressing law of conservation of momentum in the flow, equation for conservation of discharge and differential equation for nonuniform motion of transit flow with the account of tangential turbulent stresses on lateral surfaces. As opposed to the existing solutions, we accounted for the presence of two regions of spreading with different slopes of water surface, horizontal component of fluid weight, nonuniform distribution of velocities in head section, high roughness and the case when sections of target and vertical contraction do not match. Satisfactory results were obtained by comparing theoretical solution and experimental data.