To address the difficulty in self-starting for vertical-axis water turbines with fixed pitch angles and to improve the efficiency of marine energy utilization,a hybrid power generation device was proposed that incorporated a Savonius-type wind rotor to assist in starting the vertical-axis water turbine.Numerical simulations were conducted to investigate the dynamic output characteristics of this integrated device.Firstly,a three-dimensional two-phase flow numerical tank was constructed using Fluent software,and the mesh partitioning scheme was determined by comparing the values of the power output parameters of the device under different mesh densities,and at the same time,the validity of the numerical tank was confirmed.Secondly,the established numerical tank was used to simulate the variation law of torque,speed and power coefficient of power generation devices under different flow field conditions with different water wheel blade numbers,radius ratios and height ratios.The results show that the device performs better in terms of torque stability,speed characteristics,and energy utilization in the simulated working condition range when the water wheel blades are 3 to 4,the radius ratio is 0.25 to 0.375,and the height ratio is 1/6 to 1/3.The device is able to start quickly in the presence of wind,and the power coefficient reaches 0.3 to 0.4 or even exceeds 0.4,with good starting and power generation performance.The research results can provide a reference for the design and application of the device.
The performance of Autonomous Underwater Vehicles(AUVs)is significantly influenced by their shape design.This study presents a novel AUV shape optimization method that integrates data-driven approaches and machine learning technique to focus on the impact of the head and tail profiles,and the configuration of the fins and rudders on AUV performance.A parameterized hydrodynamic analysis workflow was developed to automatically generate the hydrodynamic parameters required during the optimization process.Based on this workflow,a data-driven framework was constructed for multi-objective optimization of AUV shapes,with the aims of minimizing drag and maximizing maneuverability.Surrogate models for the two optimization objectives above were built using Multilayer Perceptron(MLP)neural networks and ensemble learning methods respectively,and their performances were compared with traditional surrogate models.The optimization problem was solved using the Non-dominated Sorting Genetic Algorithm II.Comparative analysis of the initial and optimized AUV shapes demonstrates significant improvements in hydrodynamic performance,confirming the feasibility and effectiveness of the proposed method.
In this study,the influence of opening parameters on the ultimate strength of perforated plates subjected to extreme cyclic loading in the presence of material kinematic hardening and isotro-pic hardening was analyzed.It is found that the ultimate strength of the perforated plates decreases rapidly and stabilizes in the first four cycles.Plates with oblong openings have a greater ultimate strength compared to plates with rectangular openings,while the relative strengthening ratio decreases over the duration of the cycle.The location of the openings is also an important parameter that affects the strength of the structure,as the plates with openings close to the edges in the longitudinal direction have higher strengths,while in the transverse direction the strengths are higher when the openings are close to the center.Among the three opening-strengthening methods compared,the Carling stiffener method maintains a better strengthening effect under cyclic loads for many periods.
There are numerous wave energy resources in the ocean, and how to convert them efficiently is still a problem to be solved. Considering the waves in China sea area are characterized by short period and small height, one new model combining three split heave point absorbers with a tension leg platform (TLP) is proposed in this paper. Based on the physical model test, the hydrodynamic performance and wave energy capture efficiency of the split absorbers are investigated, and compared with those of the corresponding unsplit absorber. The experimental results reveal that the split absorber presents new hydrodynamic characteristics, and that the efficiency of the new wave energy capture device is greatly improved for small-period waves in the low sea state. However, the pitch motion of the platform is significantly increased in some cases with specific incident wave direction, which needs to be solved by further optimizing the TLP mooring system.
Liquid sloshing is a common phenomenon in ocean engineering, and one which not only affects the stability of ship navigation, but also poses a threat to both the marine environment and human life. Ascertaining how best to reduce the amplitude of liquid sloshing has always been a key problem in ocean engineering. In this study, based on an improved moving-particle semi-implicit method, the BM-MPS method, the damping effect of a vertical slotted screen under rotation excitation was simulated and studied, and the influence of baffle porosity and the rotation amplitude on the resonance period and impact pressure was discussed. The results showed that the porosity had an obvious effect on the resonance period. A significant resonance period transformation happened when the porosity was 0.1, but a porosity of 0.15 was the point at which the maximum impact pressure in the resonance was at its minimum. Meanwhile, the impact duration curve was related to porosity. With the increasing of porosity, the impact duration curve changed from having no peak to a single peak, and then to double peak. In addition, the amplitude of rotation excitation was also one of the factors that affected the resonance period.
