【正文】 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 4 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 the tunnel).The initial design of the Rogunskii hydroelectric plant called for a chute as the terminus structure of the operational spillway。 moreover, the lower the level of the water surface, the more the air restrained the water flow and transformed the flow into a rotation node (Fig. 7). Stable vortextype flow with a peripheral water ring and internal gasvapor core is formed beyond the tangential vortex generator. Due to asymmetric delivery of water into the vortex generator in the initial segments, the core of the flow is noncircular and situated away from the center of the cross section. Throughout the length of the initial cylindrical segment of the conduit, the gasvapor core possesses a wavelike curved axis which coincides with the axis of the tunnel even as close as 10dx from the axis of the shaft. As nonaerated flow enters the tailrace conduit through the rotation node, a vacuumgauge pressure is established in the gasvapor core, and in the case of highly aerated flow, gauge pressure, The reduction in pressure in the gasvapor core is associated with the effect of centrifugal forces in vortextype flow, while an increase in pressure is associated with nearly plete release of air from the aerated flow into the core induced by the transport of air bubbles from the periphery to the center under the effect of the pressure gradient. For a tailrace conduit with cylindrical initial segment, the free area downstream increases from in the section at a distance from the axis of the shaft to in the section at a distance , while the angle of flow rotation and the axial and circumferential flow rates all decrease. In the case of a conical initial segment, the relative area of the gasvapor core decreases from to over the length of the conical segment, while the angle of flow rotation decreases to between onehalf and twothirds its initial value over this segment. A characteristic feature of the construction that is being proposed in the present article is the presence of an energy dissipation chamber in which vortextype flow experiences an abrupt expansion and is rapidly transformed into axial flow if the discharge of flow from the tailrace tunnel is directed into the of the centrifugal acceleration to the free fall acceleration is an essential condition for breakdown of thevortex structure of the flow in the tunnel. Once equality is achieved, the mass of water traveling along the roof of the tunnel caves in, and mixes easily with the air in the flow core. The transformation of vortexlike flow into axial flow that occurs here is acpanied by significant dissipation of