Umar Farooq

This study examines the complex three-dimensional (3D) air-water flow characteristics in a chute spillway using Ansys Fluent for numerical simulations. The Volume of Fluid method incorporating a dispersed interface and Large-Eddy Simulation was evaluated along with the Renormalization Group k-ε model for comparative analysis. Based on available experimental data, the numerical model was validated using two structured grids: Uniform Structured Mesh (USM) and Locally Refined Structured Mesh (LRSM). The approach velocity was v = 6.831 m/s, corresponding to a Froude number of 7.525 and a Reynolds number of 1.313 × 10 ⁶ , measured upstream of the aerator. The analysis was conducted in two stages: (i) an assessment of mesh refinement and (ii) an evaluation of LES sub-grid-scale (SGS) models. The numerical results demonstrate that both procedures reproduce the general trends of flow pattern, jet length, velocity, and pressure along the chute. However, pronounced differences arise in the prediction of air concentration within the cavity and reattachment zone. Among the investigated approaches, the Locally Refined Structured Mesh coupled with SGS models provides better agreement with experimental results, capturing flow patterns, pressure distribution, air concentration in the cavity, and the downstream region with reasonable accuracy. The Uniform Structured Mesh and RNG k-ε exhibit larger deviations in terms of flow pattern, velocity, pressure, and air concentration. The findings demonstrate that aerated spillway flow predictions are more sensitive to grid resolution than to SGS modelling configurations.

The updated flood guidelines in Sweden have led to higher design discharges for many existing dams. While the primary function of a spillway chute is to convey floodwater, roughness appurtenances are proposed for installation along the chute. The aim is to dissipate an extra portion of the flow’s energy before release into the tailwater. One straight and three labyrinth roughness configurations are designed and manufactured. Their effectiveness is assessed through model tests. The roughness leads to an increase in water depth and induces an undulating streamwise water-surface profile. Due to their lateral interaction with the flow, the labyrinth shapes exhibit less distinct contours of surface unevenness than the straight one. With an increasing water depth, the free surface becomes gradually smeared out. For all the shapes, the roughness effect on the surface flow almost disappears if the water depth exceeds 6.5–7.0 times the roughness height. Compared to the smooth chute, the straight elements augment the energy loss by a factor of 1.9–3.8; the labyrinth configurations outperform the straight ones by 16–35% more energy dissipation. The differences among the triangular, trapezoidal, and rectangular shapes are, however, minor. Introducing chute roughness is a complementary measure. If the chute is sufficiently long, an adequate number of roughness rows could replace the function of a stilling basin.

The hydraulic performance of pooled stepped spillways has received less recognition compared to the traditional stepped spillways. Regarding the effectiveness of pooled stepped spillways in managing flow dynamics, previous studies have focused on investigating how different step configurations and varying chute angles can enhance energy dissipation in gravity flow over the chute. However, the potential for optimal performance and the importance of proper design have not been thoroughly explored in the existing literature. This study aims to explore new configurations of pooled stepped spillways and compare them to traditional stepped spillway designs to enhance hydraulic efficiency and maximize energy dissipation. The study examines two types of configurations of stepped spillways—two flat and two pooled configurations, each with ten steps. Using the computational Fluid Dynamics (CFD) technique, such as Volume of Fluid Method (VOF) and the realizable k-ε turbulence model for two-phase flow analysis with a 26.6° chute slope. Initially, the model was validated with experimental data by comparing various hydraulic parameters. These parameters include water depth, roller length, jump length, ratio of critical depth, and sequent depth. The hydraulic performance of both stepped geometric configurations was evaluated through numerical simulations to examine how the geometries of flat and pooled stepped spillways influence flow characteristics, energy dissipation, velocity, pressure distribution, and the Froude number at the downstream. The study analyzed downstream flow characteristics, maximum energy dissipation rates, depth-averaged velocity, static pressure, and pressure contours at the lateral direction under six different flow rates in flat and pooled stepped spillways. The findings indicate that flat-step configurations exhibit lower energy dissipation compared to pooled configurations. The relative energy loss of flow on pooled steps dissipates more energy than on flat steps. Furthermore, it is observed that the pooled configurations performed better for energy dissipation and flow stability compared to the flat configurations. The energy dissipation increased in pooled stepped spillways by 34.68% and 25.81%, respectively. Additionally, the depth-averaged flow velocity and pressure distribution decreased in case 2 and case 4 compared to the flat-step configurations.

The soil water retention curve (SWRC) is a vital soil property used to evaluate the soil’s water holding capacity, a critical factor in various applications such as determining soil water availability for plants, soil conservation and management, climate change adaptation, and mitigation of flood risks. Estimating SWRC directly in the field and laboratory is a time-consuming and laborious process and requires numerous instruments and measurements at a specific location. In this context, various estimation approaches have been developed, including pedotransfer functions (PTFs), over the past three decades to estimate soil water retention and its associated properties. Despite the efficiencies, PTFs and semi-physical approach-based models often have several limitations, particularly in the dry range of the SWRC. PTFs-based modeling has become a key research topic due to readily available soil data and cost-effective methods for deriving essential soil parameters, which enable more efficient decision-making in sustainable land-use management. Therefore, advancement and adjustment are necessary for reliable estimations of the SWRC from readily available data. This article reviews the evaluation of the current and past PTFs for estimating the SWRC. This study aims to evaluate PTF techniques and semi-physical approaches based on soil texture, bulk density, porosity, and other related factors. Additionally, it also assesses the performance and limitations of various common semi-physical models proposed and developed by Arya and Paris, Haverkamp and Parlange, the Modified Kovács model by Aubertin et al., Chang and Cheng, Meskini-Vishkaee et al., Vidler et al., and Zhai et al. This assessment will be effective for researchers in this field and provide valuable insight into the importance of new PTFs for modeling SWRC.