The use of “erosion-free” energy absorbers operating during cavitation without the formation of cavitation erosion extends the use of energy absorbers and diffusers at high flow rates, removing or reducing cavitation restrictions. Considering that energy absorbers are effective means of preventing dangerous malfunctioning currents in the downstream, they make it possible to increase the water level and reduce the cost of fastening the downstream. Give the opportunity to expand the scope of their application should be taken into account when designing. Dampers of this type were used at the spillways of the Shamkhor and Artyom waterworks.
The article discusses the results of numerical studies of the flow movement with a sharp change in the parameters of the channel. Basically, the results of the study using the system of two-dimensional equations of hydrodynamics-Saint-Venant are analyzed. The divergent form of two-dimensional equations describing the movement of a water stream at a site of regulation of a channel by protective and regulatory dams is given. The influence of the length step on the results of numerical experiments is investigated numerically. Graphs of the time variation of the longitudinal velocity component behind the sudden double expansion of the channel are compiled. The flow was unsteady all the time and had the character of stationary pulsations, and the finer the grid, the richer the spectrum of these pulsations. It was noted that in numerical calculations, the time step in the calculations was always much less than the minimum pulsation period, therefore, these pulsations were not associated with difference oscillations that can arise when approximating by central differences. It is concluded that, according to the authors from the following and the present work, they collectively show that the pulsations on different grids differ significantly, the average values of the velocities are close, and thereby the solution for the average values is well converged, this shows that the pulsations are a property source equations of Saint-Venant. The applicability of the numerical model, consisting of two-dimensional shallow water equations, the vector equation of momentum conservation and the scalar equation of mass conservation, in description the flow with the presence of circulation zones, which is typical when water flows are constrained by protective-regulatory structures. In this case, the solution pulsates around a certain average value, and the average length of the circulation zone behind the sudden expansion of the open flow is in good agreement with the laboratory experiments of G.L. Mazhbits.
The article discusses various types of new improved dam water intake hydroelectric systems, sedimentation facilities, sediment control devices on rivers and canals with a rational layout. The results of the analysis of studies on the use of the theory of transverse circulation and methods of artificial, active regulation of the structure of the water intake flow are presented, which has become widespread in world practice and is the main one for creating an effective design of water intake headworks for pumping stations and hydropower facilities that provide them with reliable protection from sediments. The author of the article, on the basis of numerous experimental data obtained in various countries of the world, makes a conclusion about the effectiveness and prospects of using front-type structures with more than 50% water intake. The design of water intakes of this type has been significantly improved; they can be successfully used in various conditions, including on Mountain Rivers. The author draws attention to the development of a new design of the pioneer ditch, which ensures the efficient passage of bottom sediments into the downstream of the structure, which prevents intensive silting of the reservoir basin by bottom sediments and improves the efficiency of the dam water intake.
Presents the results of hydraulic studies in pressureless and pressure water conduits, the results of which showed that the dependences obtained for calculating the hydraulic resistance in round pressure pipes cannot be distributed without the corresponding adjustments of pressureless channels (provided that the diameter of the pipe is replaced in the corresponding calculations with a value where hydraulic radius). In particular, it follows (and this is confirmed by the data of the corresponding experimental studies published in the literature) that in the case of pressureless channels, the pressure loss coefficient, and therefore the pressure loss, depends not only on the relative roughness and Reynolds number, but also on the shape of the cross section the channel. Moreover, if for hydraulically smooth pressureless channels this dependence can be considered to a first approximation clarified, then for channels whose wetted surface is characterized by the presence of a certain roughness, the question of its influence, as well as the shape of the channel cross section on the pressure loss, is far from roughly approximate solution. The paper also considers the general equation of fluid motion in pressureless channels and the functional dependences of the coefficient of hydraulic friction on the Reynolds number, relative roughness, and on the shape of the living section of the channel; resistance formulas are first for the simplest with respect to the cross-sectional shape of the channels (round and infinitely wide rectangular), and then for channels with a more complex cross-sectional shape. To take into account the effect (on the pressure loss) of the channel cross-sectional shape and the presence of a flow with a free surface in it, additional correction factors are introduced (using the hydraulic radius concept) as well as new dependencies and formulas for determining the hydraulic friction coefficient are given, s taking into account the influence of morphometric elements of the channel on the hydraulic resistance of the machine channels of pumping stations.
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