Ertian Hua

The plain river network is characterized by low and flat terrain and a complex structure, resulting in slow water exchange and weak hydrodynamic conditions. To address these issues, a flapping-hydrofoil water pump driven by composite harmonic motion is proposed to promote water flow. First, a computational model for the flapping hydrofoil is established based on the finite volume method (FVM) and overlapping dynamic mesh technology. Five different distributed motion schemes for the flapping-hydrofoil devices at various points are selected, and the hydrodynamic performance of each scheme is computed to establish the corresponding relationship with water flow. Next, the river network of the Nanxun District in the Taihu Lake Basin is taken as the study area. A MIKE21 two-dimensional hydrodynamic-water quality model for river networks is constructed, where water flow is used as a variable factor. The objective function focuses on minimizing energy consumption under different motion schemes. The model is used to simulate and analyze the flow field distribution and water quality changes under different scenarios, aiming to explore optimization scheduling methods for enhancing hydrodynamics and improving water quality in the river network of the study area. The results show that, compared to the five motion schemes, the propulsion efficiency is maximized in Scheme IV, with a value of 49.34%. This represents a 1.12-fold increase in water propulsion efficiency compared to Scheme I (single flapping-hydrofoil motion). However, considering the water quality improvement, Scheme I exhibits the best effect in terms of flow increment. Under the conditions of Scheme I, the BOD (Biochemical Oxygen Demand) removal rate at the reference point 2 area reaches 40.94%, and the DO (Dissolved Oxygen) concentration improvement rate reaches 1.78 times.

To address the issues of insufficient hydrodynamics and water stagnation in plain river network areas, this study focuses on the typical river network of the Nanxun Campus of Zhejiang College of Water Resources and Hydropower. It aims to optimize the deployment and determine the operational parameters of a bionic hydrofoil pumping device. A 2D hydrodynamic model is built using MIKE21 to simulate flow field characteristics under various conditions, including different placement positions, with or without water-blocking measures, and combinations of flow rate, water level, and flow direction. The impacts of these conditions on system head loss and river velocity are analyzed. Results show that the optimal setup involves deploying the device near the pump house with water-blocking measures, at a flow rate of 1 m³/s, a designed water level of 2.55 m, and a counterclockwise direction. This setup maintains a river velocity of no less than 0.02 m/s, meeting daily water circulation needs. The target hydraulic parameters (flow rate of 1.0 m³/s and head of 0.084 m) are used to propose a similarity theory for hydrofoils, establish scaling relationships, and derive the minimum operational frequency of three serial bionic hydrofoil pumps at 0.268 Hz under this setup. To inhibit algal growth during special periods, the velocity is raised to 0.15 m/s, requiring an increase in frequency to 2.008 Hz. These findings offer a theoretical basis and engineering support for the application and operational parameter design of bionic hydrofoil pumping devices in complex river networks.

To improve the pumping performance of biomimetic flapping-wing devices in small river channels, this study introduces high-frequency disturbances in the heave direction based on traditional pitch–heave motion. A systematic investigation of the forces and hydrodynamic performance is conducted using numerical simulations, with vortex contour analysis to explore the evolution mechanism of the wake vortex structure. The results show that high-frequency disturbances cause the instantaneous thrust to exhibit an amplitude modulation feature, with thrust oscillating approximately f_p/f_b times within one base frequency cycle. As the disturbance frequency increases, the average thrust also increases. There is a significant frequency-dependent difference in performance: at low disturbance frequencies (f_p/f_b ≤ 16), changes in thrust, pressure difference, and flow rate are limited, with little improvement in pumping efficiency; at intermediate frequencies (16 < f_p/f_b ≤ 32), wake coherence and jet momentum flux are significantly enhanced, and both thrust and pumping efficiency reach their maximum (up to 47%); at high disturbance frequencies (f_p/f_b > 32), although the vortex structure is further strengthened, input power increases sharply, leading to a decrease in efficiency. Overall, moderate disturbance frequencies can effectively enhance the thrust and pumping performance of the flapping wing, while excessively high frequencies do not offer an advantage due to the high energy cost.

To address the inherent complexities of underwater operating environments and achieve the design of a highly efficient, energy-saving flapping hydrofoil, this paper proposes an intelligent agent-based model for real-time parametric optimization. A non-parametric surrogate model based on a Multilayer Perceptron (MLP) is established using data samples of multi-dimensional flapping hydrofoil geometric parameters obtained through Computational Fluid Dynamics (CFD) simulations. An improved Double Deep Q-Network (DDQN) algorithm incorporating Pareto frontier information is deployed within the surrogate model to obtain the Pareto optimal solution set for propulsion efficiency and average input power, and a set of propulsion parameter combinations with error ranges between 0.24% and 1.27% across continuous intervals was obtained. Experimental results demonstrate that the proposed MLP-DDQN method is capable of learning the domain-wide optimal solution within the experimental environment, satisfying the Pareto optimality between propulsion efficiency and average input power. Further analysis of the flow field around the flapping hydrofoil under the obtained optimal parameter combination revealed that the presence of stable and continuously attached vortex structures on the wing surface is the intrinsic mechanism responsible for its superior propulsion performance.

To investigate the impact of flexible versus rigid bioinspired flapping hydrofoils on the discharge characteristics of suspended particles in raceway aquaculture, this study established a two-way fluid–structure coupling model of a flapping hydrofoil device based on ANSYS Fluent and Transient Structural modules. The research compares the discharge characteristics of hydrofoils with different elastic moduli. The results show that, within a certain range of elastic moduli adjustment, flexible bioinspired hydrofoils exhibit greater surface deformation compared to rigid ones, effectively delaying tail vortex shedding and extending its duration, thus prolonging the range of high flow velocities. During the middle stage of discharge, the escape rate of suspended particles under the influence of flexible bioinspired hydrofoils with 0.05 GPa elastic modulus was 3–4% higher than that of rigid hydrofoils. However, in terms of achieving maximum discharge efficiency and effectiveness, both reached approximately 97.8% with little difference between them. This study highlights the bioinspired principles in hydrofoil design and provides a reference for optimizing flexible hydrofoil discharge characteristics in future research.

The bionic pumping system can effectively improve the hydrodynamic conditions in plain river networks, thereby mitigating the frequent algal blooms in these regions. This study employs numerical simulations to investigate how heave amplitude and chord length affect the hydrodynamic performance of both multi-hydrofoil and single-hydrofoil systems. The operating frequencies for the two configurations are selected by combining these results with the flow velocity threshold required to suppress algal blooms. The results show that the pumping efficiency of the multi-hydrofoil system increases with chord length and heave amplitude, and the optimal parameter combination is c = 0.18W and h_max = 0.7c. For the single-hydrofoil system, efficiency first rises and then falls, peaking at c = 0.16 W and h_max = 0.6c. Under the algal bloom suppression threshold of 0.15 m/s, the multi-hydrofoil system meets the criterion across the entire cross-section at 0.10 Hz, making it suitable for raising flow velocity throughout the water body and for comprehensive bloom suppression. By contrast, the single-hydrofoil system produces an uneven wake with lower velocities in the upper region, so even at higher operating frequencies, it cannot cover the entire cross-section; it is therefore more appropriate for localized velocity enhancement and localized suppression of algal accumulation.

This study aims to optimize bionic hydrofoil propulsion performance and establish design guidelines for efficient transmission mechanisms by comparing three mechanisms (crank-slider, cylindrical cam, and synchronous belt drive). Through 3D modeling, virtual assembly, and ADAMS simulations, dynamic responses of slider displacement and driving force/torque were obtained, revealing that the crank-slider consumes the least energy, followed by the cylindrical cam, with the synchronous belt being the most energy-intensive. Further CFD analysis demonstrated that while the crank-slider generates drag intermittently, the cylindrical cam and synchronous belt sustain continuous thrust. All mechanisms achieve effective water propulsion below their critical frequencies (0.25 Hz, 0.75 Hz, and 1.4 Hz, respectively). Propulsion efficiency peaks at 26.0% (crank-slider) and 24.7% (cylindrical cam) at 0.25 Hz but declines at higher frequencies, whereas the synchronous belt reaches 24.3% efficiency at 1 Hz with superior frequency adaptability. The synchronous belt emerges as the optimal solution for efficient flapping propulsion due to its motion continuity and frequency adaptability. This work elucidates the critical impact of transmission mechanisms on hydrofoil hydrodynamics, providing foundational insights for mechanism design and performance optimization.

To improve hydrodynamic conditions and self-purification in plain river networks, this study optimized an existing hydrofoil-based pumping device and redesigned its flow channel. Using the finite volume method (FVM) and overset grid technique, a comparative numerical analysis was conducted on the pumping performance of hydrofoils operating under simple harmonic and quasi-harmonic flapping motions. Based on the tip vortex phenomenon observed at the channel outlet, the flow channel structure was further designed to inform the structural optimization of bionic pumping devices. Results show both modes generate reversed Kármán vortex streets, but the quasi-harmonic mode induces a displacement in vorticity distribution, whereas that of the simple harmonic motion extends farther downstream. Pumping efficiency under simple harmonic motion consistently outperforms that of quasi-harmonic motion, exceeding its peak by 20.2%. The pumping and propulsion efficiencies show a generally positive correlation with the outlet angle of the channel, both reaching their peak when the outlet angle α is −10°. Compared to an outlet angle of 0°, an outlet angle of −10° results in an 8.5% increase in pumping efficiency and a 10.2% increase in propulsion efficiency.

A flapping hydrofoil device is an innovative device for enhancing the hydrodynamics of small rivers. While increasing the flow velocity of the river, it inevitably causes different degrees of scouring on the bank slope. This study aims to find an optimal combination of flapping hydrofoil parameters to maximize the pushing-water performance while minimizing the impact on bank slope scour, which is of great significance for the device’s application and environmental protection. Based on the finite volume method and overlapping dynamic grid technology, this paper selects the maximum bank slope scouring section as the research plane for numerical simulation. In order to expand the scope of application, the relative chord length c* (the ratio of chord length to river channel width) is introduced as a research parameter, and the influence of different relative chord lengths c* and frequencies f on the pushing-water performance of the device and the degree of bank slope scouring is systematically analyzed. The research results show that the near-shore current mean scouring force increases significantly with the increase in f and c*. The pushing-water efficiency will increase with c*, and will gradually increase with the increase in f and then tend to be stable. When c* = 1/2 and f = 2.5 Hz, the pushing-water efficiency reaches 51.04%, but at this time, the impact on bank slope scour is the most serious. When c* is reduced to 1/8, the bank slopes are not scoured even at the maximum frequency f = 2.5 Hz, and the pushing-water efficiency is 24.59% at this time. As c* decreases, the threshold frequency at which scour does not occur on the riverbank increases gradually. In addition, when c* is constant, decreasing f will significantly reduce the scouring force, but will have little effect on pushing-water efficiency. In order to achieve the purpose of this study, the parameters of flapping hydrofoil are recommended to be larger relative chord length and smaller motion frequency combinations.