Hydraulic modeling of surface vortex funnels

Abstract

Abstract The peculiarities of the operation of entrance portals for concrete and corrugated metal road pipes, water intake pipelines, spillway structures and hydroelectric power plants include the formation of surface vortex funnels. The formation of surface funnels reduces the water consumption in the pipeline, provokes the destruction of the fastening of the slopes at the inlet, the suction of sludge, ice and debris into the pipeline. It is desirable to avoid these phenomena. The article is devoted to the issues of physical modeling of surface funnels. The aim of the research is to determine the criteria for the breakthrough of the air core of the surface funnel into the pressure pipeline. As a result of research, it was found that the formation of vortex funnels in the upper basin is determined by the structure of the flow in the local area adjacent to the water intake. It is shown that the profile of the free surface of the vortex funnel and its depth on the axis of rotation are determined by the intensity of the circulation generating the funnel. A formula is obtained for calculating the limiting depth of a surface vortex funnel with an accuracy sufficient for engineering calculations. It is shown that in physical modeling according to Froude’s defining criterion, the depth of the funnel obtained on the model should be recalculated for a full-scale object with a scale factor m −1.5, where m is the linear scale of the model. Another method for obtaining the depth of the funnel on the model, corresponding to its conversion to a full-scale object on a linear scale, is forcing the current velocities by m−3/14 times in relation to their value according to the Froude criterion.