ASSESSMENT OF ENERGY LOSSES IN NARROWING CHANNELS UNDER CONDITIONS OF UNSTEADY FLOW

Abstract

This paper presents an improved hydraulic model for analyzing unsteady flow behavior in variable cross-section open channels, with particular focus on converging rectangular inlet chambers. The study aims to enhance the accuracy of hydraulic computation under non-stationary conditions by incorporating the influence of vortex structures and gradual contraction geometry. Experimental investigations were carried out using a laboratory model with a converging rectangular channel of 120 cm length, 80 cm inlet width, and outlet widths of 40, 35, 30, and 25 cm. Average flow velocity was maintained near 0.67 cm/s, and four discharge rates of 30, 25, 20, and 15 𝑚3/ℎ were analyzed. Flow velocities were measured using a micro-propeller current meter. The results showed that increasing flow discharge and shortening contraction length both intensify vortex formation. The proposed model improves flow prediction accuracy by up to 8% compared with classical steady-state approaches and provides recommendations for optimizing inlet chamber geometries in open-channel systems.