HYDRAULIC ASSESSMENT OF FLOW IN STEPPED AND LABYRINTH SPILLWAYS TO DETERMINE ENERGY LOSS USING A PHYSICAL MODEL

A 'spillway' is a structure used to provide controlled release of flood water from upstream into downstream area of a dam. As an important component of every dam, a spillway should be constructed strongly, reliably, and efficiently to be used at any moment. Labyrinth and stepped spillways are presented as appropriate modifications to those spillways hardly capable of managing maximum potential discharge. Owing to their nonlinear crests for a given width, labyrinth and stepped spillways have a larger discharge rate than linear-crest spillways at an identical height. Compared to other energy dissipaters, the combination of stepped and labyrinth spillways is known as a very strong energy dissipater. In the following part, the combination of these two structures and their dimensional change for increasing water-energy dissipation are addressed. To conduct this laboratory study, an experimental flume with a 90-degree bend in the Islamic Azad University of Ahwaz was used. In total, 90 experiments were conducted on three different labyrinth-shape stepped spillway models with two different lengths, three different widths, and five different discharges. Analysis of results showed a greater energy loss reduction in triangular than rectangular than trapezoidal labyrinth -shape stepped spillways. In addition, energy loss is greater in labyrinth spillways with two cycles than with one cycle. Energy loss increases by increasing the Froude number from 0.05 to 0.1; whereas energy loss decreases with increasing the Froude number from 0.1 to 1.0, which is due to the submergence of steps, a decrease in roughness of steps, and an increase in the intensity of aeration.