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Wave-Powered Reverse Osmosis (WPRO) represents a promising convergence of ocean energy harvesting and advanced Reverse Osmosis (RO) desalination techniques. The significant fluctuations in pressures and flow rates within the integrated WPRO system present a critical challenge, necessitating an accurate transient model for effective performance estimation. This study presents a two-dimensional transient model based on pressure-correction algorithm to simulate channel flow with membrane boundary conditions under varying inlet conditions. The coupled dynamics of pressure, velocity, and salt concentration are addressed iteratively by decoupling and updating each term separately. The model investigates the performance of RO systems under different input conditions, including constant, sinusoidal, and irregular flow. The results indicate that constant input with higher pressure and lower flow rate achieves a better Recovery Ratio (RR). It is emphasized that for WPRO systems, a fair comparison requires choosing the same average power or pressure when evaluating different inputs. Under equivalent input power, sinusoidal waves result in a lower RR compared to constant inputs due to reduced average pressure. Conversely, under equivalent inlet pressure and flow rate, sinusoidal waves achieve a higher RR than constant inputs due to the phase difference between pressuredriven permeate velocity and diffusion-driven Concentration Polarization (CP). Specifically, sinusoidal inputs with higher frequency and higher amplitude display a higher RR. Additionally, irregular input yields a higher RR than constant inputs, as mean pressure and power can be maintained at levels comparable to those of constant input. The model’s adaptability to diverse flow regimes — from steady to sinusoidal and irregular fluctuations — highlights its potential as a critical tool for optimizing RO desalination processes powered by renewable ocean energy. 

Abstract Ocean wave-powered reverse osmosis (RO) desalination is an emerging field of study that combines the utilization of ocean energy and RO desalination techniques. However, due to the significant fluctuations in pressure and flow rate within the hydraulic system, an accurate transient model is necessary to estimate its performance accurately and effectively. This paper presents a two-dimensional transient model based on the pressure-correction algorithm to simulate the channel flow with porous walls and time-dependent inlet conditions. The coupled pressure, velocity, and salt concentration problem is solved iteratively by decoupling each term and updating them separately. The model is validated by comparing the results with analytical film theory which estimates the formation of the concentration polarization layer under constant inlet conditions. The performance of the RO systems, especially the concentration polarization phenomenon at the member surface, is investigated using different input conditions, including constant flow condition and sinusoidal flow condition. The salt concentration and permeate flux at the membrane boundary are studied to understand the effect of the dynamic inputs. Results show that the system can reach a higher maximum wall concentration and higher average recovery ratio in sinusoidal signal compared with the constant input. The model’s adaptability to different flow regimes, from steady to sinusoidal, underscores its potential as a valuable tool in optimizing RO desalination powered by ocean wave energy. 

This study presents an analysis of the fatigue damage experienced by mooring systems under extreme and operational wave conditions, with a discussion on the Reference Model 3 (RM3), a widely recognized point absorber wave energy converter (WEC), and the Reference Model 5 (RM5), a floating oscillating surge wave energy converter (FOSWEC). Utilizing the combined strengths of WEC-Sim and MoorDyn, both open-source simulation tools, the study investigates the dynamic behavior of mooring lines over the operational wave condition and a 100-year return period extreme wave condition. This study highlights the relationship between tension force and fatigue damage in mooring lines. The tension forces at various nodes of the mooring lines are calculated, revealing that the complex mooring design is causing a complex trend on the fatigue damage. Instead, variations in tension force show a more significant impact on cumulative fatigue damage, as evidenced by the higher damage observed in nodes experiencing greater tension variation. The findings contribute to a better understanding of the factors influencing fatigue damage in mooring lines of WECs and fatigue damage of different types of WECs, offering insights for more effective monitoring and strategies for WEC design optimization. 

Abstract Thermoelectric generators convert heat energy to electricity and can be used for waste heat recovery, enabling sustainable development. Selective Laser Melting (SLM) based additive manufacturing process is a scalable and flexible method that has shown promising results in manufacturing high zT Bi2Te3 material and is possible to be extended to other material classes such as Mg2Si. The physical phenomena of melting and solidification were investigated for SLM-based manufacturing of thermoelectric (Mg2Si) powders through comprehensive numerical models developed in MATLAB. In this study, Computational Fluid Dynamics (CFD)-based techniques were employed to solve conservation equations, enabling a detailed understanding of temperature evolution within the molten pool. This approach was critical for optimizing processing parameters in our investigation, which were also used for printing the Mg2Si powders using SLM. Additionally, a phase field-based model was developed to simulate the directional solidification of the Mg2Si in MATLAB. Microstructural parameters were studied to correlate the effects of processing parameters to the microstructure of Mg2Si.