【正文】 g of the tailrace segment, and, as a consequence, flow rates of slightly vortextype and axial flows through the subsequent legs that do not produce cavitation damage. On the other hand, the dangerous effect of high flow rates on the streamlined surface decreases over the length of the initial tailrace leg as a consequence of the increased pressure on the wall caused by the effect of centrifugal forces. A number of structural studies of tunnel spillways for hydraulic works such as the Rogunskii, Teri, Tel39。 it was intended that the flow rate at the end of the chute was to reach 60 m/sec. Understandably, flow rates that are this high entail adoption of special measures to protect the streamlined surfaces of the spillway from cavitation damage and the stream course from dangerous degradation. To meet this need, the Tashkent Hydroelectric Authority, working with the Division of Hydrodynamic Research (now the Central Hydraulic Institute, Society of the Scientific Research Institute on the Economics of Construction), developed several alternative versions of spillway designs intended to dissipate a significant portion of the energy of the flow within the spillway and to substantially reduce the flow rate in the tailrace tunnel and at the point where the flow is discharged into the stream course. In one of the versions that were considered, the bend in the turning segment that is part of the traditional configuration of a shaft spillway was replaced by a tangential flow vortex generator. Similarly. vortextype flow is created throughout the entire length of the tailrace segment. Hydraulic studies were performed on a model that simulated a shaft spillway at a scale of 1:50 and consisted of a shaft measuring 13 m in diameter and 148 m in height, a tangential vortex generating device, and a tailrace tunnel. The studies that were performed showed that in the shaft which delivers water to the flow rotation node, an intermediate water level is maintained when the flow rate is less than the design rate. This bench mark depends on the magnitude of the escapage discharge and the resistance of the spillway segment situated at a lower level . In the constructions that have been considered here, maximum (design) flow rates through the shaft are achieved when the shaft is flooded and there is no access to the air. In the model nearly plete entrapment of air from the water surface occurred with intermediate water levels in the shaft。 in particular, techniques are now available for calculating the hydraulic resistance of individual legs of a route and the flow rates and pressures in vortextype flow. However, for each actual hydraulic project a designed structure must also be evaluated by means of model investigations, since it is still not possible to evaluate all the elements of the operation of a spillway by means of calculations. Thus, let us turn our attention to a number of theoretically important problems. A familiarity with these topics will be of assistance in the design and investigation of vortex spillways. Evaluation of the Design and Geometric Dimensions of the Elements of a Spillway. The selection of a particular type of spillway depends on a number of factors, such as the effective head, the magnitude of the escapage discharge, the configuration of the hydraulic project (for example, the use of a river diversion tunnel during the operational period or of the water conduits of hydroelectric power plants in the construction period), conditions in the discharge of the flow into the tailrace channel, topographic and geological features (in particular, the possible length of the tailrace leg), and the technical and economic characteristics.