In this study, a fully compressible, two-component, three-phase cavitation model was employed to investigate the interaction between cavitation bubbles and air bubbles confined within a finite-volume cavity. The focus was on understanding how an entrapped gas bubble influences cavitation dynamics, including bubble morphology, collapse intensity, the evolution of the secondary Bjerknes force, and the Kelvin impulse. Results show that at smaller wall-to-bubble distances (L), cavitation bubbles exhibit asymmetric growth due to interface intrusion into the air bubble, leading to earlier micro-jet formation and severe air bubble deformation. Rebound of the air bubble during collapse accelerates the micro-jet, enhancing jet velocity, though this effect weakens with increasing L. Larger cavity radius and depth reduce air bubble fragmentation and bottom pressure while maintaining collapse pressure. A power-law relationship was observed between the maximum collapse pressure and velocity and the dimensionless parameter ζ, highlighting the roles of cavity geometry and wall distance. Additionally, the secondary Bjerknes force exhibits significant fluctuations at smaller L, indicating strong mutual coupling between cavitation and air bubbles. These findings offer insights into optimizing gas-containing, cavitation-resistant structures through geometry control.

Dissolved oxygen (DO) is a vital water quality index influencing biological processes in aquatic environments. Accurate modeling of DO levels is crucial for maintaining ecosystem health and managing freshwater resources. To this end, the present study contributes a Bayesian-optimized explainable machine learning (ML) model to reveal DO dynamics and predict DO concentrations. Three ML models, support vector regression (SVR), regression tree (RT), and boosting ensemble, coupled with Bayesian optimization (BO), are employed to estimate DO levels in the Mississippi River. It is concluded that the BO-SVR model outperforms others, achieving a coefficient of determination (CD) of 0.97 and minimal error metrics (root mean square error = 0.395 mg/L, mean absolute error = 0.303 mg/L). Shapley Additive Explanation (SHAP) analysis identifies temperature, discharge, and gage height as the most dominant factors affecting DO levels. Sensitivity analysis confirms the robustness of the models under varying input conditions. With perturbations from 5% to 30%, the temperature sensitivity ranges from 1.0% to 6.1%, discharge from 0.9% to 5.2%, and gage height from 0.8% to 5.0%. Although the models experience reduced accuracy with extended prediction horizons, they still achieve satisfactory results (CD > 0.75) for forecasting periods of up to 30 days. The established models also exhibit higher accuracy than many prior approaches. This study highlights the potential of BO-optimized explainable ML models for reliable DO forecasting, offering valuable insights for water resource management.

Anabranching river systems, characterized by multiple stable channels separated by vegetated islands, play a crucial role in maintaining aquatic biodiversity. Despite their ecological significance, anabranches' influence on ecohydraulic environments and fish habitats remains largely unexplored. This study seeks to address the gap by offering an in-depth investigation into the habitat dynamics and sensitivity of anabranching rivers, aiming to enhance the understanding of anabranches’ ecological suitability, resilience, and stability. For this purpose, the study establishes an ecohydraulic framework to assess the habitat status for target species in four anabranching reaches with distinct channel complexity. The main channels provide optimal habitats for species favoring dynamic environments at moderate to high flows. In contrast, the low-energy anabranches provide refuges during extreme flows, supporting species that rely on stable and low-velocity conditions. The study also highlights the critical role of channel complexity in sustaining ecological resilience; reaches with complex anabranching patterns and vegetated islands provide higher habitat stability across a wide range of hydrological scenarios, mitigating the impacts of extreme events on aquatic habitats. Long-term ecological predictions demonstrate that anabranching channels enhance ecological stability, with limited fluctuations in habitat quality. From a management perspective, this study advocates for conservation practices that preserve these multi-channel structures and hydrological connectivity, supporting sustainable habitat conditions under changing environmental pressures. This research offers valuable insights for managing anabranching rivers and contributes a framework for habitat assessment applicable to similar ecosystems.

A stilling basin is a critical hydraulic structure designed to dissipate excess energy from high-velocity flow exiting a spillway, preventing erosion to downstream channels. Despite its significant role in dam safety, lining damage of stilling basins occurs frequently, due to gaps and offsets between slabs and undersized underdrains. This study employs a CFD approach to examine how these factors affect flow dynamics and uplift forces. Different scenarios are examined, combining varying gap widths, offset heights, and vent configurations, under three flow rates for each. Results reveal that gap width minimally influences uplift forces. Offset heights considerably enhance upliftpressures, with a 10% increase when offset height doubles from 1.5 cm to 3 cm. Venting reduces uplift pressures effectively by facilitating water escape beneath slabs, with larger vent sizes yielding negative uplift pressures. However, venting intensifies pressure fluctuations, with the pressure coefficient rising substantially, particularly at higher flow rates. This study contributes to a deeper understanding of damage mechanisms and offers valuable insights for upgrading and rehabilitating such structures.

The Darcy–Brinkman model at the representative elementary volume scale is utilized to examine the hydrodynamic characteristics of the dam-break wave’s impact on a porous medium. Factors influencing the impact of hydrodynamic processes, including porosity and wave propagation mode, are systematically analysed. The results indicated that the maximum dimensionless water intrusion volume shows a linear relationship with porosity. Under different dam-break wave modes, the impact pressure exhibits distinct pressure evolution curves. For bore-like waves on a wet bed, a double-peak distribution is reported correspond to the impact of the breaking wave and the following main flow. In contrast, for dam-break waves on a dry bed and undular waves on a wet bed, only a single pressure peak can be observed. Finally, the maximum total force of dam-break impact on the upstream surface of the porous medium displays a linear relationship with porosity, for a consistent downstream water depth.

An innovative semi-analytical approach is devised to evaluate the dynamic characteristic of a friction-type pipe pile partially packed with soil plugs, subjected to time-harmonic seismic P-waves in a homogeneous soil medium. In this model, the shaft is conceptualized as a hollow structure with inner soil acting as continuum. The soil beneath the pile's vertical projection is viewed as a distinct soil pillar, while the surrounding soil and the column are collectively modeled as a uniform continuum. By examining the energy interactions between the inner soil and the pile-soil system and leveraging the Hamilton’s variational principle, the governing equations for both the shaft and the soil pillar, along with the interface contact requirements, are established. The attenuation characteristics of the surrounding soil are also derived. The solution employs variable separation techniques and an iteration methodology to resolve the coupled equations, satisfying the pile-soil system’s boundary and continuity constraints. This leads to a frequency-domain semi-analytical formulation for the seismic responses of the system. The accuracy of the developed solution is substantiated by comparing it with established results. Subsequently, numerical analyses are conducted to explore how varying material and geometric parameters impact the seismic interactions between the pile and soil.

A hybrid thermal lattice Boltzmann cavitation model based on a nonorthogonal framework is developed to investigate the interaction of two attached-wall cavitation bubbles. The interaction modes are systematically analyzed, with an emphasis on how varying contact angles influence the flow and temperature distributions, as well as the evolution of wall heat flux under strong and weak interaction conditions. Bubbles formed on the hydrophobic surface display increased contact radius and greater curvature radii compared to those on the hydrophilic wall, leading to greater volumes but weaker collapse intensity. The growth rate of the bubble equivalent radius for the weak interaction modes consistently follows the relation U∝2p∞/3ρl. Additionally, bubble coalescence occurs at the interface regions along the hydrophobic surface, altering the final collapse dynamics and resulting in distinct temperature and velocity distributions. Finally, the instantaneous heat flux characteristics are explored. Due to differences in the contact points motion rate and microjet angle with the solid wall, the peak value and number of heat flux peaks vary on walls with different wettability.