【正文】 oject are of decisive importance in deciding which energy dissipation scheme to adopt. 。 and for the Rogunskii spillway, Ar:q = . A second parameter which characterizes the degree of rotation of the flow on individual legs of the tailrace segment is the integral flow rotation parameter II [1, 2]. The prerotation 17 0 behind the vortex generating device at a distance from the axis of the shaft may be determined on the basis of graphical dependences thus: 17_o = f(A) (Fig. 4).Tailrace tmmd. The overall widths of the tunnel are determined by the type of spillway design which is selected and the method decided on for dissipation of the excess energy (either by means of smooth or increasingly more intensive dissipation). Energy Dissipation Chamber. The choice of design and dimensions depends on the rate of rotation of the flow at the inlet to the chamber and on the length of the tailrace tunnel following the chamber. For a tailrace tunnel with LT/d T _ 60, it is best to use a converging tube (or cylindrical) segment as the conjugating element between the tangential vortex generator and the energy dissipation chamber. The segment will be responsible for the following functions: reduction of the rate of rotation of the flow at the inlet to the energy dissipation chamber, equalization of flow rates acpanied by a shift in the maximum axial ponent of the flow rate into the central portion, and reduction of the dynamic loads at the rotation node of the flow. From the foregoing discussion it follows that in those cases in which there is no entrapment of air, vortex spillways may be modeled with respect to all the required criteria. The situation is different in the case of aerated flow, which is also difficult to model. In hydraulic models with external atmospheric pressure, the volumetric content of air varies slightly as the flow is transported down the shaft to the critical section, whereas in the physical structure, the entrapped air, moving downwards, is pressed by the increasing pressure of the liquid. Thus, in the case of the spillway at the Teri hydraulic works (Fig. 1), the percent pression in the physical structure is as much as 15fold, whereas in the open model constructed on a 1:60 scale, the percent pression is in the range , ., onetenth that of the values found in the field. Moreover, in the experiments using the models, there was an increase noted in the angles of rotation of the flow in the initial segment of the tailrace tunnel as the escapage discharge was decreased and the content of air in the mixture was increased. Inasmuch as in the physical object the air content in the critical section is always insignificant, the increase in the angles of rotation as the volume of escapage discharge was decreased was unexpected. To create a reliable model of vortextype flow when there is a free level in the stem of the shaft and abundant air entrapment by the flow, it is necessary to isolate the region of air in the upper and lower ponds from the external atmosphere and to reduce the air pressure in these regions through creation of a vacuum in accordance with the geometric scale of the model. Hydraulic Conditions throughout the Spillway Segment. The hydraulic conditions of operation of vortex spillways differ substantially from the corresponding conditions for spillways constructed in the traditional configuration. Let us consider these differences on the basis of the results of laboratory studies of the operational spillways of the Rogunskii hydroelectric plant (which includes an energy dissipation chamber) and the spillway of the Teri hydraulic works (which operates with smooth dissipation of energy throughout the length of