Performance Assessment of Anti-Vortex and Stepped Chamber Modifications in Morning Glory Spillways via Computational Modelling

Shaft spillways are a specialized type of circular spillway primarily utilized for the controlled release of unplanned floodwaters, commonly used at earth and concrete dams, the spillways are considered as vital components in flood management. For this type of shaft spillway, the stepped spillway and smooth spillway is the most common spillways. Specifically, the almost realistic high flow rate in stepped spillways indicates the importance of determining the unsteady flow patterns and behaviours in order to optimize the design for efficient performance. The effect of these devices upon flow dynamics is a critical aspect of full-scale spillway design and operation, as vortex breakers significantly affect these dynamics, thus warranting their inclusion in the design process. Cavitation is a major concern when operating a spillway, as this phenomenon can cause the flow pressure to fall below the vapor pressure of the fluid and lead to severe damage of the structure. In order to this, the current investigation deals with the analysis of the cavitation index for smooth shaft spillways and compares the cavitation index with one type of stepped spillway. Understanding how varying flow patterns, step dimensionality, and flow types influence spillway functionality is the focus of the current research. Among them, two different models, a smooth and a stepped one, were tested with three different configurations of vortex breaker, making a comprehensive characterization of the hydraulic behaviour and cavitation risk. At different inlet discharges, pressure and flow velocity were measured at several sites along the surface of the spillway during experiments. The analysis of dimensionless parameters across various locations on the stepped spillway, which contributed towards cavitation risk assessment, included the step height-to-width ratio (h/b), the overall quantity of steps, and distance from the spillway's initiation point. These variables were quantified using both theoretical and numerical methods. The results of the conducted process revealed that the studied stepped spillway has properties of the ۱۲-th variant of it, which is the most cavitation resistant and resistant against concrete erosion.

کلیدواژه ها:

: Vortex breaker ، flow ، Stepped Chamber ، Comsol soft ware