Оценка пропуска минимальных расходов воды сооружениями дюкерного типа мелиоративных систем

Abstract

Issues related to the design and hydraulic calculation of the transit part of a closed tubular water supply structure of the siphon type is considered. The operating conditions of the siphon with rectangular pipes in the transition mode are evaluated, in which the entrance section of the pipes of the culvert structure experiences increased hydrodynamic loads, often leading to certain destructions. The siphon design was modeled with two breaks along the length with a smooth inlet head and without a head. During the experiments, the absence of infl uence of the inlet head of the tubular HTS on the length of the free-flow section was noted. It has been established that the conditions of formation and features of the hydraulic operation of the siphon in the transient mode are largely determined by its design features. With the flooding of the inlet head, the flow of air into the pipe is hindered and a transition mode of the second type is formed with a slight fluctuation of the water level in the upper pool. The dependence of the location of the point of separation of the flow with a decrease in the passing water flow rate on its value is revealed, which made it possible to obtain a graph of the dependence of the relative length of the non-pressure end section on the square root of the Froude number. A comparison was made with the results of studies by other authors, which showed an increase in the relative length in tubular HTS of the siphon type in sections with reverse slopes at the same Froude numbers. Recommendations are given on the methodology for carrying out hydraulic calculation of tubular structures of the siphon type with minimal flow rates.