Hydrodynamic assessment of body exposure in drainage stairways: a numerical study

Abstract

This work presents advances in the study of nappe flows in stepped chutes, focusing on scenarios without the formation of hydraulic jumps on the steps. The dynamics of flows in "drainage ladders", which are structures that serve as both pedestrian pathways and open channel for surface waters, was analyzed using the k- turbulence model, multiphase inhomogeneous model, and high-resolution numerical schemes. Two aspects were focused: the drainage capacity of the ladder and the resultant force exerted on a foot/leg-like obstacle located on a step of the flow. Calculation domains in two and three-dimensions were used. The two-dimensional simulations allowed quantifying the energy dissipation of the nappe flow regime without the sequential hydraulic jumps. The results include dimensionless relationships between the residual specific energy and the depth of the flow, which show adherence to experimental data from the literature and points to the suitability of the proposed methodology for the numerical modeling of the problem. Furthermore, due to the allowed partial channel flow, the numerical results show that the drainage use of the ladders significantly reduces the horizontal forces acting on the human-form obstacles on the steps, with 31.9% of reduction for the studied scenarios.