The object of research is the issue of studying the hydraulic process of fluid movement in open free-flow channels. As is well known in hydraulic engineering construction, open flume-type conduits are widely used, where the flow velocity sometimes exceeds the critical ones. Therefore, it is necessary to determine the main hydraulic parameters of the fluid flow in a turbulent regime. Of particular interest is the movement of the flow in the rotary part of the tray. Method. To determine the main hydraulic parameters of the flow in the turning part, we proceeded from the Euler equation for the polar coordinate system. Taking into account the Bernoulli equation and subsequent integration of the main formula, calculation formulas for the turning part of the flow were obtained. Result. Because of the study, we obtained the main expressions by which the turning radius can be determined and compared with the critical one. These parameters allow you to analyze the turbulence of the flow in the tray.