Search

The oscillating hydrofoil, a device used for collecting environmentally friendly tidal energy, is the focus of the study. The flexibility of the hydrofoil's trailing edge can impact its surface pressure distribution, lift, and moment characteristics. To improve the energy harvesting performance of oscillating hydrofoils, it is important to conduct thorough research on their energy harvesting mechanism. Therefore, numerical analysis is employed to develop a numerical model of the fully passive oscillating hydrofoil with the flexible trailing edge. The dynamic development behavior of surface vortices on hydrofoils is analyzed, demonstrating that the fluid–structure interaction between the hydrofoil and the surrounding fluid alters the hydrofoil's motion. The vortex patterns and pressure distribution on the hydrofoil surface are also affected, ultimately influencing the energy harvesting performance. By optimizing the flexibility coefficient of the fully passive oscillating hydrofoil with a flexible trailing edge, the energy harvesting performance of the oscillating hydrofoil is improved. When the maximum chord offset δm= 0.1c and the flexibility coefficient n = 2, the energy harvesting efficiency is 31.37%, and the average power coefficient is 1.17. Therefore, increasing the tail flexibility can be considered to enhance energy harvesting performance when designing the fully passive oscillating hydrofoil. The research provides a comprehensive analysis of energy harvesting performance, addressing the dynamic problem of the fully passive oscillating hydrofoils with flexible trailing edges. The findings of this study may provide guidance for the design and optimization of tidal energy harvesting devices with similar structures. [ABSTRACT FROM AUTHOR]

In this work, a multi-output model is proposed based on extreme learning machine, which uses the regression information of training samples and the correlation of outputs to predict multiple responses for the new point. Two kernel matrices are designed to evaluate the regression relationship of training samples and the correlation of the outputs, respectively. A five-fold cross-validation method is used to assess the training error, and a heuristic algorithm is used to optimize the hyperparameters of the proposed model. The results of mathematical problems indicate that the performance of the proposed model is better with more training samples and is positively correlated with the correlation of outputs. The proposed model produces more competitive performance in terms of prediction accuracy and computational cost than the benchmark multi-output models. The proposed multi-output model is applied to the multi-objective optimization of a dental implant, showing its application potential in engineering design and optimization. [ABSTRACT FROM AUTHOR]

Extremely complex flow channels and multi-parameter, highly nonlinear thermal fluid–structure interactions are the main factors restricting the exploration mechanism and optimal design of explosion-proof valves. To overcome these problems, comprehensive numerical research is performed in this paper, particularly concerning the method of valve dynamic modeling, and surrogate model-based design optimization. First, numerical models are presented; a dimensionality reduced computational fluid dynamics modeling method is proposed, using two approaches to simulate the blocking effect of flame-retardant sheets. Their accuracy is verified using both steady and transient simulations, which indicate that the equivalent volume is more accurate than the equivalent porous method. Second, to improve the flame-quenching ability of the explosion-proof valve, surrogate modeling-based design optimization is performed. In optimization, three structural parameters are selected as design variables and the extended adaptive hybrid functions (E-AHF) surrogate model is used as the predictive model. Based on the developed surrogate model, a genetic algorithm is implemented to identify the optimum structure of the flame-retardant sheets. To verify the performance of the optimized design, 3D steady-state simulations are performed. The results indicate that the cooling effect of the optimized scheme on the high-temperature gas is increased by 12.21%. [ABSTRACT FROM AUTHOR]

An acoustic black hole (ABH) has the ability to concentrate and manipulate flexural waves, which can be used for structural vibration suppression and noise attenuation. In this paper, a 2D ABH rectangular plate is designed and a 2D ABH plate-cavity coupling system is constructed using the 2D ABH plate and five rectangular elastic plates of uniform thickness. Series of vibro-acoustic FEM models of the plate-cavity parallelepiped coupling system embedded with 2D ABHs are established, and the vibro-acoustic coupling simulation is conducted to analyze the effects of ABHs on the coupling modes, vibro-acoustic coupling characteristics, and mechanism of ABHs and the damping layer. It is shown that at most frequencies in the range of 3600~5000 Hz, the damping 2D ABH plate-cavity parallelepiped coupling system can significantly suppress the sound pressure and greatly reduce the peak values. It is also found that the significant reduction of the participation factor of the acoustic modes within the 100th order is the main mechanism for the obvious suppression of the sound pressure in the damping ABH plate-cavity coupling system at 3701 Hz. Finally, an experimental platform of vibro-acoustic measurement of the 2D ABH coupling system is constructed, and the accuracy of the vibro-acoustic FEM models of the 2D ABH coupling systems established in this paper and the numerical simulation calculation are verified by the vibro-acoustic measurement experiment. [ABSTRACT FROM AUTHOR]

The acoustic black hole (ABH) structures have the potential to achieve structural vibration suppression and noise reduction through the effect of the ABH on the concentration and manipulation of flexural waves. In this paper, a new solution is proposed to embed 2-D ABHs on the support plate to suppress the transmission of compressor vibration to the refrigerator body. The vibration and acoustic measurement experiment of the compressor, the support plate and the refrigerator body, and the coherence analysis of the vibration signals and acoustic signal are carried out to determine the influence of the compressor vibration on the vibration of the refrigerator body and the radiation sound of the back wall. The concentration and manipulation effects of 2-D ABH on flexural waves are verified by numerical simulation of flexural wave propagation in the time domain. FEM models of the original support plate and the damping ABH support plate are established to investigate the comprehensive effect of the 2-D ABHs and the damping layers on the vibration characteristics of the support plate through vibration modal and dynamic response analysis. Numerical simulation results show that the 2-D damping ABHs can suppress the vibrations generated by the compressor at specific frequencies in the middle and high-frequency bands from being transmitted to the refrigerator body through the support plate. [ABSTRACT FROM AUTHOR]