Determination of the optimal modes of filling and emptying the chamber of the navigational lock of a low-pressure hydroelectric complex

The construction of the low-pressure Nizhny Novgorod hydroelectric complex covered by the Strategy for the Development of Inland Water Transport of the Russian Federation for the period up to 2030 envisages a ship lock as part of the hydroelectric system to ensure ships passage. One of the options under consideration is a ship lock with a head power system, which uses short bypass water-circulating culvert for filling and emptying the chamber. At the same time, an important task is to select the optimal modes ensuring movement of the gates of the filling and emptying systems, in which the normative values of the hydrodynamic forces influencing the vessel in the chamber during the lock process would not be exceeded. The article describes the experience of performing laboratory hydraulic studies of the ship lock model and presents the results of determining the optimal modes of locks movement in the ship lock filling and emptying systems. The studies were carried out on a model located in the hydrotechnical laboratory named after Professor V.E. Timonov of the State University of Maritime and River Fleet named after Admiral S.O. Makarov. The article describes the experience of performing laboratory hydraulic studies of the ship lock model and presents the results of determining the optimal modes of gates movement in the ship lock filling and emptying systems. The studies were carried out on a model located in the hydrotechnical laboratory named after Professor V.E. Timonov of the State University of Maritime and River Fleet named after Admiral S.O. Makarov. The studies included three series of measurements taken at different speeds of gates movement. The speeds were assigned based on the following idea: the maximum hydrodynamic forces of one of the series were close to the permissible values, and of the other two – 30–50 % smaller and larger, respectively. The experimental results determined the optimal operating modes of the systems for filling and emptying the lock chamber. It is recommended to select of the optimal modes of gates movement in full-scale conditions on the newly built ship locks immediately after their construction.

Analysis of metothods determining the value of the flow’s speed when entering the lock chamber

The purpose of this work is to compare the results of calculating the velocities of the flow around the ship's hull when it enters the lock chamber using various methods. The article presents the mathematical dependences obtained by various authors in the course of their research depending on the coefficient of constraint of the lock chamber by the ship's hull. An attempt to determine the influence of the height of the wave that arises in front of the stem in the process of entry which creates a slope of the water surface and the effect of this factor on the speed of the flowing stream is made. It was found that the values ​​of the flow velocities calculated by various methods have discrepancies. And the methods themselves do not allow determining the speed of the flow around when large-tonnage vessels enter the lock chamber of an extremely small width. The authors proposed a simple technique for calculating the flow velocity for cases of large values ​​of the constraint coefficient using an auxiliary graph.

Analysis of methods determining the value of the vessel’s critical speed when entering the lock chamber minimum width

The paper presents an analysis of analytical dependencies to determine the value of the critical speed of the vessel when entering the lock chamber. It is presented the analysis of analytical dependences for determining the value of the critical ship’s speed when entering the lock chamber, obtained by various authors earlier in the course of model and full-scale tests. The main factors affecting the safety of the approach process are noted. It was established that the critical velocity values calculated by various methods give a spread of values. However, some of them do not allow determining the value of the critical speed when the vessel enters the lock at high values of the constraint coefficient. It is indicated that the safe and effective speed of entry into the lock depends on the speed of the stream flowing around the hull of the vessel, which, in turn, is determined by the height of the shear wave in front of the ship’s bow (i.e., the slope of the free surface of the water). These factors lead to the conclusion that further research is necessary