INFLUENCE OF THE DEGREE FLOODING AND COMPRESSION CROSS-SECTION OF A HYDRAULIC STRUCTURE WITH UNSTEADY LIQUID MOVEMENT

Abstract

The article is devoted to topical issues of the influence of hydraulic structures on the behavior of channel flow. Issues related to the operation of hydraulic structures located on irrigation canals were considered: - the influence of the degree of flooding on the elements of unsteady movement in open channels; - the influence of flow compression on the elements of unsteady motion in open flows. Quantitative assessment of the impact degree of flooding and compression on the elements of the flow during steady motion was carried out taking into account the recommendations of prof. Bolshakova VO, which are based on the use of the method of prof. Vasilieva OF The question influence of hydraulic structures on the behavior of the channel flow was solved using the equations of Saint-Venan by the numerical method, namely the method of run by the implicit-difference scheme. To close the system when using this method, the following conditions were taken into account: a - initial; b - left and right boundary conditions. The initial conditions are the presence of uniform movement in the channel. The left boundary condition is determined by the schedule of water supply to the channel, which has the form of a triangular hydrograph. The right boundary condition is determined by the known formula of a spillway with a wide threshold. The initial data were obtained from field observations. Quantitative assessment of the impact of flooding and flow compression on the final flow, velocity and depth results was performed. The issue of distribution of the support along the channel bed, which was formed due to the compression of the flow, was solved using the recommendations of E.V. Eremenko. The equation of flow continuity was considered - under the condition of changing the volume of water in the elementary section of the channel. The time of increase in the volume of water due to compression was determined from the formula obtained in the calculation process. Based on the condition that the time factor is a known value, it is possible to obtain a mathematical expression that determines the length of the propagation of the compression effect. Thanks to the obtained formulas, the calculated graphs of the relative maximum depth depending on the degree of flooding were constructed. With the help of these graphs it is possible to solve the problem of water supply in irrigation canals in the presence of flooding and compression of the flow (in case of unsteady movement).