The geometric shape of a buoy is crucial in enhancing the efficiency of wave energy harvesting. However, comparative studies are often compromised by inconsistent design constraints—particularly the failure to maintain identical natural frequency—which obscures the pure effect of geometry. Therefore, this paper proposes a novel S-shaped buoy characterized by three parameters l, α, β, and ensures all buoys are designed with identical diameters, submerged volumes, and resonant frequencies to perform a fair geometric comparison under the same dynamic conditions. Based on wave conditions of the Paracel Islands, six S-shaped buoys with distinct parameter combinations and identical resonant frequencies were evaluated under regular waves, irregular waves, optimal and suboptimal power take-off (PTO) modes. Results show that SB-b buoy (l = 2.6 m, α = 120°, β = 120°) exhibits the best comprehensive performance. Its power absorption under the optimal PTO mode outperforms that of the ellipsoidal and conical buoys by 4.9

This study aimed to enhance the particle separation efficiency of suspended particulate matter in pond aquaculture tailwater by designing a combined hydrocyclone-filtration device. A solid-liquid two-phase flow numerical model was developed using CFD method, and its accuracy was validated via physical scale-model tests. The effects of the structural parameter (column section length), operational parameter (inlet flow rate), and filter material property (filter layer thickness) on flow-field characteristics and particle separation efficiency were systematically analyzed. Key findings revealed that separation efficiency first increased and peaked at a column section length of 450mm before decreasing; an elevated inlet flow rate enhances vortex intensity and separation efficiency; an increased filter layer thickness improves efficiency by strengthening the vortex. The results demonstrate that increasing column section length initially improves separation efficiency up to an optimal value before decreasing, while higher inlet flow rates enhance vortex intensity and separation performance. Increased filter layer thickness strengthens tangential velocity and promotes particle separation. This research provides a theoretical foundation for applying hydrocyclone-filtration devices in tailwater particulate removal, offering quantitative insights into the individual effects of column length, flow rate, and filter layer thickness, which may inform future design optimization and practical implementation in aquaculture wastewater treatment

To improve the stability of the deep-sea aquaculture cages, a numerical hydrodynamic model of a Rotatable Horizontal Aquaculture Cage Platform (RHACP) was developed based on three-dimensional potential flow theory and the Morison model. After verifying the reliability of the numerical simulation, this study focuses on analyzing the hydrodynamic characteristics, including heave, pitch, and surge, as well as the mooring forces of the RHACP at 3 different draft depths (9, 13, and 17 m). The results show that an increase in draft reduces the mooring line tension and the platform motion response. The heave and pitch responses of the RHACP are positively correlated with both wave height and wave period, whereas the surge response is positively correlated with wave height but negatively correlated with wave period. At an incident wave angle of 90 degrees, the RHACP exhibits greater resistance to extreme sea states than that at 0 degrees.

Small spherical microphone arrays are widely used for three-dimensional sound field measurements due to their compactness and omnidirectional response. However, their performance in low-frequency sound source identification and localization is limited by aperture constraints and the ill-conditioned inverse problem inherent in spherical near-field acoustic holography (SNAH). This study proposes an Equivalent Source Method–Spherical Near-field Acoustic Holography (ESM-SNAH) algorithm. The method constructs a virtual large-aperture spherical array using the ESM, which improves the condition number of the propagation matrix and enhances spatial sampling in the spherical harmonic domain. Leveraging the computational efficiency of SNAH in this domain, the approach enables accurate low-frequency sound source identification and localization. In addition, a multi-parameter coupled optimization strategy is introduced for selecting equivalent source parameters, further stabilizing the reconstruction process. Simulation and experimental results demonstrate that the ESM-SNAH algorithm achieves improved low-frequency source identification and localization compared to conventional SNAH, exhibits enhanced dual-source resolution within a certain frequency range, and shows relatively strong robustness against noise and parameter variations under typical operating conditions. The proposed framework effectively mitigates the physical-aperture limitations of compact arrays and offers a practical solution for compact-array-based low-frequency acoustic measurements and imaging. A novel ESM-SNAH method for sound source identification and localization is proposed. Performance comparison of SNAH and ESM-SNAH based on simulation and experimental analysis. Sound source identification and localization performance with two-error combined evaluation. The ESM-SNAH algorithm is applicable to relatively complex real-world acoustic environments.

Taking the Deep Blue No. 2 aquaculture cage as the research object, this study calculates frequency-domain added mass and damping coefficients via the boundary element method, generates external function files with time-domain parameters and equivalent ballast net weight via the power-based averaging method, and imports them into a time-domain solver based on the Cummins equation to simulate 6-DOF motion responses during submergence. Numerical results agree well with flume model tests, verifying that the method accurately reproduces three characteristic submergence stages: initial submergence stage, acceleration stage, deceleration stage. Furthermore, motion responses under different environmental conditions are analyzed. At a 5 m wave height, the overall drift exceeds a quarter of the aquaculture cage characteristic length. In the acceleration submergence stage, peak pitch responses and peak drift displacements at 10 and 12 s wave periods are 15%–25% higher than those at the 14 s period. Current velocities below 0.62 m/s induce no significant differences in motion responses during the submergence process. Under wave-current coupling loads, hydrodynamic load dominance shifts through three stages: combined wave-current action, wave dominance and current dominance. Motion responses under emergency submergence are 1.6–4.6 times those under normal operating conditions.

Recirculating aquaculture system (RAS) represents a key direction for the transformation and upgrading of pond aquaculture. However, their structural design lacks sufficient theoretical basis, resulting in low hydrodynamic circulation efficiency. Furthermore, the sedimentation, diffusion and aggregation behaviors of particulate matter such as uneaten feed and fish feces in RAS remain poorly understood. In this study, a novel Partitioned recirculating aquaculture pond (PRAP) was innovatively designed based on Computational fluid dynamics (CFD), employing the Shear stress transport (SST) turbulence model and the Discrete phase model (DPM). A full-domain hydrodynamic numerical model of the pond was established and validated against experimental data. First, the hydrodynamic characteristics of the full pond and high-density culture zone were analyzed, including velocity distribution, flow uniformity index, and the evolution of turbulent vortex structures. The movement trajectories, distribution patterns and escape rates of particulate matter were investigated, and the influence mechanisms of particle density and size were examined. The study shows that the PRAP system exhibits excellent hydrodynamic characteristics and pollutant collection efficiency. Internal partitioned baffles form distinct recirculation zones, effectively eliminating stagnant dead zones. The full-domain flow uniformity index reaches 0.78 at an inlet flow rate of 28.27 m³/h. Significant velocity differences exist across pond regions: the central aeration zone has a local average velocity exceeding 3 m/s for efficient circulation; the filter-feeding culture zone maintains velocities below 2 m/s, matching the feeding physiology of silver carp, bighead carp and associated organisms; the high-density culture zone has a stable average velocity of 0.04 m/s, suitable for carnivorous fish. The waterwheel aeration zone generates vorticity of 2.5–3.6 s⁻¹, enhancing dissolved oxygen levels. The aquatic purification zone accumulates more particles, promoting ecological cycling between particulates and vegetation. Particle escape rate decreases with increasing size, while removal efficiency decreases with increasing density.

To enhance the pollutant removal efficiency in the Recirculating Aquaculture System (RAS), a sewage suction pipe is typically installed in the Recirculating Aquaculture Tank (RAT), connecting the underflow port and tank wall. Its primary function is to remove particulate pollutants accumulated at the tank bottom, such as feces and uneaten feed. In this study, an octagon-shaped dual-channel RAT in actual operation was used as the research object. A multiphase flow numerical model was established based on the two-phase flow theory, and the accuracy of this model was validated through physical scale-model experiments. Key hydrodynamic parameters, including flow velocity, vorticity, and water mixing uniformity, were systematically investigated. Meanwhile, the pollutant discharge rates at the underflow port and suction pipe outlet were quantitatively analyzed to evaluate the system’s pollutant removal efficiency. The results showed that the sewage suction pipe significantly affects the rotational flow field and vortex structure inside the RAT: As the angle of the suction pipe increases, the velocity gradient near its water inlet decreases, which weakens the tendency of particulate matter to aggregate toward the RAT center and thus hinders particulate discharge. Additionally, the diameter of the suction pipe exerts a notable impact on the flow velocity in the RAT: When the pipe diameter increases, the overall flow velocity and momentum transfer efficiency in the RAT decrease, the water flow uniformity index reduces, and the particulate discharge rate presents a trend of "first increasing and then decreasing".

Deep-sea aquaculture cages are prone to large motion responses under the combined effects of extreme wind, waves, and currents. In severe cases, these responses may lead to structural instability, mooring failure, or even capsizing. This study investigates the hydrodynamic stability of a horizontal aquaculture cage equipped with external floats and a multi-point mooring system through comparative numerical analysis and engineering assessment. A three-dimensional ANSYS AQWA model coupling potential-flow hydrodynamics, Morison-type loads, and a dynamic mooring-line formulation was established and benchmarked against published surge and heave response amplitude operators for Ocean Farm 1. Time-domain simulations were then conducted under a 50-year return-period wind–wave–current condition for the deep-water South China Sea to compare cage configurations with and without eight external floats and to assess four mooring layouts: bridle, cross, herringbone, and parallel. The external floats reduced the magnitude of the negative peak heave displacement by 22.9%, from 5.332 to 4.111m, and the magnitude of the negative roll peak by 45.0%, from 14.588° to 8.021°; the peak-to-peak roll amplitude decreased by 28.1%. Slight increases in some positive heave and sway responses indicated a redistribution of the coupled motion rather than uniform suppression of all response components. Under the herringbone configuration, the modules reduced tension variability and low-tension occurrence by 15.48% and 72.32%, respectively, and decreased the inter-line dispersion of mean and peak tensions by 36.50% and 16.26%, although the governing maximum tension increased by 8.42%. The parallel arrangement provided the best control of surge, heave, pitch, and yaw, whereas the herringbone arrangement performed better in sway and roll; the cross arrangement exhibited the weakest overall stability. These results demonstrate that external floats can improve cage-motion stability and mooring-load sharing, but the buoyancy and mooring systems should be designed jointly to account for the associated increase in extreme tensile demand.

Add phase change materials can significantly improve the stability of the solar water heating system, but at the same time increase the complexity of the system. To solve the design problem of the key parameters of the photovoltaic/thermal integrated air-source heat pump (PVT-ASHP) hot water system, a simulation model of the PVT-ASHP hot water system with coupled phase-change tanks based on TRNSYS was established. Taking a civil building in Zhengzhou as the research object, the influence of four key parameters of hot water collection tank volume, PVT area, inclination angle and circulation flow on system performance is analyzed. Taking overall efficiency as the goal, the influence degree of four parameters on system performance is obtained by orthogonal experiment and range analysis method, and the optimal parameters are determined. The results show that the COP of the PVT-ASHP hot water system with coupled phase change tanks can reach 3.92, which is an 18.07% improvement over the conventional PVT-ASHP system, and at the same time exhibits lower energy consumption and higher power generation performance. Among the four parameters considered, the influence degree of system performance is tank volume, PVT area, circulating flow rate and inclination angle in turn, and the overall efficiency is up to 76.28%. The research results can provide a theoretical basis for the performance optimization design of PVT-ASHP hot water system.

In the pond recirculating aquaculture system (PRAS), the paddlewheel aerator is vital for improving dissolved oxygen and hydrodynamic conditions in recirculating aquaculture tanks (RATs). Understanding its influence on the hydrodynamic characteristics of RATs can enhance energy efficiency, improve sewage collection, and ensure uniform dissolved oxygen (DO) distribution. This study focuses on a 15 m side length chamfered RAT in a partitioned PRAS. The flow numerical model was validated by conducting a series of comparative analyses with the scale test model. Hydrodynamic parameters include flow uniformity, velocity, vorticity, Froude number, and effective energy utilization coefficient were analyzed. The Pearson correlation coefficient method explored the relationships between the effective energy coefficient and the aerator's placement angle and distance. Results indicate that increasing the aerator's angle and distance raises flow velocity and strengthens water mixing, promoting settleable particle discharge. But when the distance is L/4 of the RAT side length and the angle exceeds 30 degrees, a low-velocity turbulent zone forms, blocking waste particle discharge. When the distance is L/6 or L/ 4 and the angle ranges from 20 degrees to 30 degrees, energy utilization and water mixing performance improve remarkably, increasing suspended particle discharge rate. This study offers a theoretical basis for enhancing large-scale RAT operation efficiency and water quality regulation ability.

To enhance the stability of the rotatable horizontal aquaculture cage (RHAC) in marine environments, this study proposes an optimization strategy aimed at improving the primary structural configuration, while improving the motion characteristics, ensuring adequate aquaculture space. A parametric model of the RHAC is established, and single-factor experiments are conducted to analyze the effects of different net cage radius (r), net cage cone angle (alpha), and net cage length (L) on response amplitude operators (RAOs) and displacement, which refers to the movement of the center of gravity of the RHAC relative to the origin. Based on the response surface methodology (RSM), a predictive model for cage displacement and volume is constructed to elucidate the matching relationship between the main structural parameters (r, alpha, L) and stability. Three sets of optimization schemes are formed by minimizing displacement and maximizing volume as joint optimization objectives combined with single-objective optimization. The predicted values of the optimization design points are compared with corresponding numerical simulation results, with a maximum deviation of 9.04 %, which verifies the effectiveness of the optimization. The research results indicate that the stability and aquaculture space of the cage can be effectively balanced through structural parameters optimization. When r =10 m, alpha= 30.001 degrees, and L= 43.415 m, the optimization effect is optimal. Compared to the initial design, cage displacement is reduced by 10.07 %, while the volume increased by 44.70 %. Additionally, the RAOs in the sway, heave, roll, pitch, and yaw directions are significantly reduced. This study deepens the analysis of the hydrodynamic performance of the RHAC, offers theoretical support and design guidance for its engineering applications, further enhances its adaptability and aquaculture efficiency in complex marine environments

The buoy size significantly affects the wave energy captured by the point-absorption wave energy converter (PAWEC). Understanding the parameter's dynamics is critical for tailoring buoy sizes to specific sea conditions. This study employs Design of Experiments (DOE) and ANSYS AQWA software to reveal that the buoys' radius draft ratio (R/L) has a predictable impact on wave energy absorption and, for the first time, identifies the accurate threshold that affects buoy oscillation performance. Considering that the wave energy in most sea areas worldwide exhibits distinct seasonal distribution characteristics, a novel buoy optimization method is proposed to fit the specific marine environments. Taking the South China Sea as an illustrative case, the seasonal and annual wave energy absorption of buoys with different R/L are discussed in detail. Ultimately, the buoy with R = 6.5 m and L = 6 m (R/L = 1.08) is verified as the most suitable one for the sea area, providing valuable insights for practical engineering applications.

To reduce the overturning risk under extreme sea conditions, this study employs a numerical method to study and optimize the safety performance of a novel rotatable horizontal aquaculture cage (RHAC) system. The impact of buoyancy volumes on the net cage movements is analyzed using AQWA simulations and a tank experiment, indicating that the cage structure possesses a self-rotation capability under external forces. The cage rotation directions and velocities are controlled by adjusting the inflation state of the floating bodies, thereby flipping the fouled underside of the net upside down for subsequent cleaning. The effects of wave height, wind speed, and the arrangement of floating bodies on the dynamic behavior of the cage are analyzed systematically. Results show that the "single circular ring with 8 floating bodies" configuration offers superior stability, reducing approximate 75 % pitch amplitude compared with cages without floating bodies, and shows a decrease of about 4 % in longitudinal pitch angle compared with the other three configurations. Additionally, the six-degree-of-freedom motions are assessed under the four typical mooring failure states. Results show that chain breakage on one side leads to the most severe responses, inducing 90 degrees yaw, doubling vertical heave, and 8-time longitudinal surge.

To enhance the safety of aquaculture cages under extreme marine conditions and address the issue of netting biofouling, this study innovatively designed a horizontal aquaculture cage structure capable of floating, submerging, and rotating. A combined theoretical and experimental approach was adopted to investigate the hydrodynamic behavior of such cage groups under different layouts and marine conditions. Firstly, a dynamic model of the cage group was established based on the lumped mass method and Morison equation, and the rotatable performance of the cage and the reliability of the numerical model were verified through underwater tests on the physical model. Subsequently, taking the 1 x 4 layout cage group as the research object, the timedomain analysis method was used to analyze the effects of wave height and the ratio of cage spacing (L) to wavelength (7) on hydrodynamic responses and mooring tension. Finally, the nonlinear dynamic response characteristics of the 1 x 4 and 2 x 2 layout cage groups under combined wave-current action were studied. The results show that the surge, heave, and pitch motions of horizontal cage groups in floating and submerged states are significantly affected by wave height and the ratio of L/7. The submerged state can effectively suppress the pitch amplitude and reduce mooring tension. In layout design, cage spacing should be avoided to be close to the wavelength to prevent resonance and reduce the risk of extreme loads. Compared to the 1 x 4 layout, the 2 x 2 layout reduces the average standard deviation of mooring tension by 6.06 % with more uniform tension distribution. However, positive incidence of wave-current significantly increases the pitch amplitude of the rear cages in the 2 x 2 layout.

Medical protective clothing is important for maintaining the health and safety of the wearer, but its thermal comfort is poor. To improve the thermal comfort, a portable cooling device was designed and a medical protective clothing cooling system was constructed using this device. Through simulations, the actual cooling capacity of the portable cooling device was studied at various temperatures; the micro-environment temperature variation rule for medical protective clothing based on the cooling device was explored under different temperatures and activity intensities, and the cooling system's effect on the wearer's skin temperature was clarified. The results show that the temperature difference between the inlet and outlet of the portable cooling device is maintained at approximately 13 degrees C under various temperatures, the cooling power is approximately 31.2 W. After cooling system operation for 2 h, the micro-environment temperature and average skin temperature maximum drops are 6.0 degrees C and 5.6 degrees C, respectively. The system can reduce the protective clothing's micro-environment temperature and the human skin temperature effectively under various environmental temperature and activity intensity conditions. Which are of significance for verification of the feasibility of a new concept for cooling system design and the resulting improvement in the thermal comfort of medical protective clothing.

To address persistent challenges in aquaculture systems, particularly biofouling-induced reductions in water exchange efficiency and net structural degradation, this study introduces an innovative horizontally rotatable cage design. The proposed configuration incorporates bilateral airbag modules mounted on cage pressure rings, engineered to generate controlled asymmetric torque for facilitating autonomous cage rotation. The study employed a nonlinear finite element method combined with the Morison equation and the Screen model to analyze the hydrodynamic response of the cage under the combined effects of wind, waves, and currents. The numerical model's reliability was rigorously validated through benchmarking against experimental hydrodynamic data from conventional gravity cage systems. Comparative analyses revealed that under a wave height of 1.25 m, the vertical displacement of the cage at a wave period of 3.2 s was 23 % less than that at a wave period of 7.5 s, while the anchor chain tension increased by 37.5 %. Under extreme sea conditions, the axial force of the center lever was maximized when the wave direction was 0 degrees, enhancing the cage's self-rotation effect. When the wave direction was 90 degrees, the displacement amplitude was maximized, but the figure-eight mooring system was still able to maintain the stability of the cage.

To enhance the separation efficiency of particles in the rotating ceramic membrane aeration process, this study employs the Eulerian two-fluid model and the Population Balance Model (PBM) to numerically simulate the gasliquid two-phase flow within the reaction zone of the aeration device. The accuracy of the numerical calculation model is validated by comparing bubble diameters at different monitoring planes. The study investigates the impacts of different aeration rates, bubble diameters, and ceramic membrane rotational speeds on the characteristics of the two-phase flow field. The results are as follows: As the aeration rate increases, in the top part of the aeration tank, the water flow velocity and turbulence dissipation rate are relatively low, which is conducive to improving the flotation efficiency. When the aeration rate reaches 10 m3/h, the velocity and turbulent dissipation rate decreased significantly. When the bubble diameter is 20 mu m, the velocity non-uniformity index inside the aeration tank is the lowest. When the bubble diameter increases to 100 mu m, the water flow velocity and turbulence dissipation rate near the ceramic disc are at their minimum. As the rotational speed of the ceramic membrane increases from 30 r/min to 60 r/min, the flow field velocity and turbulence dissipation rate gradually decrease, while the gas content near the ceramic membrane increases significantly.

In this study, a hydrodynamic model of a semi-submersible aquaculture platform was established. The time domain motion characteristics of the platform were explored under different mooring arrangements and local mooring line failures. Moreover, comprehensive analyses were conducted to explore the factors, including spectral peak period, wave height, and current velocity on both the dynamic response of the platforms and the mooring tension. The results show that after the failure of mooring line, the influence of variations in wave height and spectral peak period on the drift motion of the platform is relatively small. In contrast, an increase in the current velocity enhances the motion. Furthermore, when the mooring lines are symmetrically distributed on both sides of the load, compared with the failure of mooring lines at the same corner, the failure of symmetrical mooring lines has a more significant impact on the platform's drift motion and mooring tension.

To address the crucial issue of optimizing the design of fairings for drag and noise reduction, this study focuses on a high-speed elevator in operation as the research subject. The numerical and experimental analysis investigates the influence mechanism of a three-sided arc fairing on the surface pressure distribution, surrounding airflow velocity, and aerodynamic drag of elevator cars. The results indicate that the fairing is effective in reducing the high-pressure area on the top of the car. It also helps to prevent vibrations caused by early separation of the boundary layer and periodic vortex separation, and mitigates the impact of aerodynamic forces on the car when there is a sudden change in airflow direction. As the arc radius of the fairing increases, the airflow velocity between the car and the shaft decreases. This leads to a reduction in the tail vortex area at the bottom of the car, resulting in decreased aerodynamic drag. Among the four schemes, scheme D with the largest arc radius of the fairing demonstrates the best optimization performance. Compared to the case without fairing, the car surface pressure decreases by approximately 35%. The aerodynamic drag is reduced to 129.51 N, which corresponds to a 60.13% decrease. However, the fairing has little impact on the lateral lift. The airflow velocity variations in the numerical simulation and experimental tests exhibit the same trend. The average relative error is about 10%, verifying the effectiveness of the numerical calculation method.