The design of a spillway, called a countereddy spillway, was,proposed and investigated at the V. V. Kuibyshev Moscow Civil Engineering Institute (MISI).The spillway (Fig. i) consists of an inlet pressure conduit 1 from which branch six conduits 2 of smaller diameter conveying water to a cylindrical chamber 7 separated by a deflector 6. The chamber with a length of 2-3 diameters passes into the outlet conduit, which can be both pressure and freeflow. The water is delivered to the chamber by conduits 2 tangentially, whereupon three conduits (section A-A) swirl the flow in one direction and the other three (section B-B) in the opposite direction.Both swirled flows, by-passing the separating deflector 6, enter the chamber, where their interaction and intense dissipation of the energy of the swirl (kinetic and pressure energy) occur. Also provided for is the entry of an axial flow into the dissipation chamber through conduit 3, which should promote stabilization of the flow and reduction of cavitation phenomena.Conduits 2 and 3 are equipped with gates 4, which can be in two positions:closed or completely open. There is also an air duct with a gate 5 through which air can be fed into the central part of the flow. The discharge is regulated by bringing into operation a various number of tangential conduits 2.An important advantage of such a spillway compared to the scheme of separating and joining two swirled flows [i] is that the zone of intense interaction of the two flows is located within the common flow and does not close up on the walls of the dissipation chamber, which eliminates the danger of occurrence of dynamic actions on the spillway structure.The swirled flows increase the pressure on the chamber walls within the limits of the deflector and tangential inlets, which promotes a decrease of velocity and prevents the occurrence of cavitation.The energy is dissipated on a short length of chamber 7.
An eddy shaft spillway is one of the common types of high-head hydraulic structures. Many such spillways have been constructed in Italy [11]. In the USSR the spillway of the Medeo mudflow-protection dam is also an eddy one [1].An eddy shaft spillway ( Fig. 1) consists of an inlet channel, spiral chamber having a box section [2], vertical shaft, bend, and outlet tunnel. The flow, entering the shaft from the spiral chamber, acquires rotation, as a result of which it is pressed against the shaft walls. Here occurs an excess pressure preventing the development of cavitation. Despite the fact that the diameter of the vertical shaft (2R) of the eddy spillway is greater than that of a circular shaft spillway with the same discharge capacity and the design of the portal is more complex, their hydraulic advantages --stable operation in the entire range of variation of the discharge from zero to the maximum --make it possible in a number of cases to give preference to a spillway of this type [2].Several methods of hydraulic calculation of eddy shaft spillways, empirical [2, 3, 12] and analytic [13, 14, 15], have been developed. Without dwelling on the first, since they have a limited applicability, we will compare the proposed analytic method examined below with the known ones and with results of experimental investigations [4, 11, 12].To determine the discharge capacity of an eddy shaft spillway, we will write the system of equations of conservation of energy, momentum, and continuity for sections I--I and II--II in Fig. 1. We will neglect the hydraulic losses due to friction in this zone. The distribution of the characteristics of the flow in the cross sections is assumed axisymmetric and in conformity with the laws of conservation of specific energy and momentum [2, 13, 15] re p where p is the water density; z 0 is the length of the zone in which equalization of the velocity distributions of the flow after entering the vertical shaft occurs and according to the data of [5] is assumed equal to 4(R --re); r e is the radius of the air core in section II--II; h is the depth of the flow in section I--I; 6 is the height of the edge at the inlet to the vertical shaft; v is the flow velocity in section I--I; Q is the discharge; v z, v r are the vertical and circumferential components of the flow velocity in section II--II, ~ is the hydraulic resistance coefficient of the edge at the inlet to the shaft, ~ = 0.11 [5]; P is the pressure in the flow in section II--II as a function of r, P = pf(vr2/r ) dr, A is the distance between the axes of the shaft and inlet channel; b is re the width of the inlet channel; p is the discharge coefficient of the eddy shaft spillway; e is the coefficient of contraction of the now (Zig. 2a [51).System (1) has the solution V ~ 4t?
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