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In order to effectively utilize the tidal current energy in offshore wind farms, a swing oscillating hydrofoil system for tidal current energy capture is proposed. The system is constructed with oscillating hydrofoils as tidal current energy capture device combined with offshore wind turbine underwater tower. Lattice Boltzmann method and large eddy simulation method were combined, and the hydrodynamic characteristics and energy collection efficiency of a NACA0015 airfoil with different motion parameters were numerically analyzed with or without the influence of tower wake. The influence of pitch amplitude, heave amplitude and chord length of the hydrofoil on the energy collection efficiency of the system is analyzed from the aspect of vortex structure in the moving process. The results show that the energy collection efficiency of the oscillating wing is significantly improved by the trailing vortex of the tower, and the vortex shedding behind the tower can reduced by the addition of the oscillating wing, consequently, the fatigue load caused by the flow around the cylindrical body can be reduced. The energy capture efficiency of the oscillating wing can reach a highest efficiently of 30.72% in the wake vortex region of the tower, which has obvious advantages compared with the traditional oscillating wing tidal current energy capture device, and provides an effective way to improve the overall energy utilization rate of offshore wind farms.

Airfoil is a key factor that influences the hydrodynamic performance of vertical axis tidal current energy turbine. In order to explore the influences from the runner’s blade airfoil towards its hydrodynamic performance, three-dimensional unsteady flow numerical simulation on four airfoils of straight blade H type of tidal current energy turbines was carried out, under the precondition of same turbine compactness. Through investigating the influences from the four different airfoils of H blade towards the runner in terms of its dynamic torque feature and hydropower utilization coefficient, this research has analyzed the hydrodynamic performance of the tidal current energy turbine. As the research result indicates, the maximum dynamic torque value of the single-blade turbine with NACA0015 airfoil is significantly higher than that of the other three airfoils; while the maximum value of the overall runner torque is determined by the operating conditions such as different stream speed etc. As a whole, hydropower utilization coefficient of the turbine with asymmetric airfoil NACA4415 is better than that of the other three airfoils. This research has provided references for the design and airfoil selection for the new type of tidal current energy turbine.

This study investigates the influence of atmospheric stability and ground effects on wind turbine wake recovery, challenging the conventional linear relationship between turbulence intensity and wake expansion coefficient. Through comprehensive field measurements and numerical simulations, we demonstrate that the linear wake expansion assumption is invalid at far-wake locations under high turbulence conditions, primarily due to ground effects. We propose a novel nonlinear wake expansion model that incorporates both atmospheric stability and ground effects by introducing a logarithmic relationship between the wake expansion coefficient and turbulence intensity. Validation results reveal the superior prediction accuracy of the proposed model compared to typical engineering wake models, with root mean square errors of wake wind speed predictions ranging from 0.04 to 0.063. The proposed model offers significant potential for optimizing wind farm layouts and enhancing overall wind energy production efficiency. [ABSTRACT FROM AUTHOR]

This study employs numerical simulation to investigate the transient flow and cavitation performance of centrifugal pumps with rough impellers, validating the numerical method with experimental data. Initially, the effect of blade roughness on the external characteristics of centrifugal pumps is examined. Subsequently, the study specifically addresses the impact of roughness on internal flow characteristics during cavitation, including vapor volume distribution, three-dimensional vortex structures, and vorticity distribution in the impeller channel. Furthermore, the influence of blade roughness on local energy loss is analyzed using entropy production theory. Finally, several monitoring points are arranged in the impeller channel to assess pressure pulsation effects. The results show that blade roughness generally reduces the head and efficiency of centrifugal pumps. During the non-cavitation and cavitation incipient stages, roughness marginally increases the head, with a maximum increase in only 0.1%. Impeller roughness causes vacuole collapse and vortex structure enlargement, disrupting the stable flow path within the channel. Blade roughness also escalates energy loss within impeller components, particularly under full cavitation conditions, where the impeller's entropy production accounts for up to 50%. Pressure pulsation results reveal that while blade roughness can slightly suppress cavitation, it also disturbs the flow field pressure. These insights provide guidance and data support for mitigating roughness and cavitation, the two primary instability factors in centrifugal pump operations. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) exhibit complex motion with multiple degrees of freedom due to the interaction of wind and waves. The aerodynamic performance and wake characteristics of these turbines are highly intricate and challenging to accurately capture. In this study, dynamic fluid body interaction (DFBI) and overset grid technology are employed to investigate the dynamic motion of a 5 MW FOWT. We use the volume of fluid (VOF) method and improved delayed detached eddy simulation (IDDES) model to investigate the aerodynamic performance and wake evolution mechanism for various wave periods and heights. According to the findings, the magnitude of the pitch motion increases with the period and height of the waves, leading to a decrease in both the power output and thrust; the maximum power was reduced by nearly 6.8% compared to a wind turbine without motion. The value of power and thrust reduction varies for different wave periods and heights, and is influenced by the relative speed and pitch angle, which play a crucial role. Wind–wave coupling has a significant impact on the evolution of both wake and vortex structures for FOWT. The wake shape downstream is also dynamically influenced by the waves. In the presence of wind and wave coupling, the interaction between the wind turbine and the wake is heightened, leading to the merger of two unstable vortex rings into a single, larger vortex ring. The research unveils a comprehensive picture of the offshore wind energy dynamics and wake field, which holds immense significance for the design of floating wind turbines and the optimization of wind farm layout. [ABSTRACT FROM AUTHOR]

Real-time scheduling methods are essential and critical to complex product flexible shop-floor due to the dynamic events in the production process, such as new job insertions, machine breakdowns and frequent rework. Recently, digital twin (DT) technology can help identify disturbances by continuously comparing physical space with virtual space, which enables real-time scheduling and greatly reduces the deviation between pre-schedule and actual schedule. However, the conventional scheduling models and algorithms cannot satisfy the adaptiveness and timeliness requirements of optimization in DT enabled shop-floor (DTS). To address above challenges, an overall framework of DT enabled real-time scheduling (DTE-RS) for complex product shop-floor is proposed to effectively reduce adverse impacts of the dynamic disturbances and minimize the makespan. Firstly, complex product flexible job shop scheduling problem (CPFJSP) is formulated as Markov Decision Process (MDP), taking into account machine breakdown and new job insertions. Then, deep Q-network (DQN) based solution is developed to achieve optimal task dispatching according to real-time production state. Finally, the case study for aircraft overhaul shop-floor is conducted to demonstrate effectiveness and feasibility of the proposed real-time scheduling method. Through experimental comparison, it is indicated that the proposed method could effectively respond to dynamic disturbances and outperform the dynamic scheduling method in terms of makespan. [ABSTRACT FROM AUTHOR]

Plant residue is an important carbon (C) source for soil communities that motivates underground C cycling. However, the effects of plant residue quantity on the structure of the soil micro‐food web and the transformation of exogenous C within the micro‐food web after increasing organic input are not known. Thus, a microcosm experiment was carried out to investigate the responses of soil micro‐food web (including microorganisms and nematodes) to different amounts of 13C‐labelled maize residue addition treatments [without residue addition, 1/3 (1/3R), 2/3 (2/3R) and total residue addition (R)]. The abundances of residue 13C in CO2 (13CO2), soil organic C (SO13C), microorganisms (13C‐microorganisms) and nematodes (13C‐nematodes) were determined after 1, 7, 35 and 84 days. Increasing organic input changed the micro‐food web composition and increased the amount of 13C‐bacteria, 13C‐fungi and 13C‐fungivores but not 13C‐bacterivores. The result of the 13C‐based network showed that bacterivores were positively correlated with omnivores‐predators at the early stage after increasing organic input, while fungivores were at the late stage. Greater 13CO2/SO13C but lower SO13C/total 13C input ratios were found in the R than in the 1/3R treatment at the early stage. At the late stage, the R treatment decreased both 13CO2/total 13C input and 13CO2/SO13C ratios. We concluded that increasing organic input strengthened the trophic interactions between microorganisms and nematodes. The transformation of exogenous C from bacteria to bacterivores might accelerate the turnover of soil C pool, however, the C flow from fungi to fungivores and then to omnivores‐predators could contribute to the exogenous C sequestration in soil. [ABSTRACT FROM AUTHOR]

Background and Aim: Gastroesophageal reflux disease (GERD) seriously lowers the quality of life of patients, and its prevalence has gradually increased in recent years. Some studies have showed that metabolic syndrome (MetS) is related to GERD, but the results remain controversial. This study explored the relationship between MetS and GERD through systematic retrieval and analysis of published studies. Methods: Retrieve related research from PubMed, Web of Science, and Cochrane Library. Including cohort studies that compare the prevalence of GERD between patients with MetS and patients without, and case‐control studies or cross‐sectional studies that compare the prevalence of MetS between patients with GERD and patients without. In addition to analyzing the relationship between MetS and GERD, individual metabolic components are also analyzed. Use a random effects model (DerSimmonian and Laird) to merge the odd ratio (OR). Cochran's Q test and Higgins' I‐squared statistic were performed to assess heterogeneity. Publication bias was assessed by Egger's test. Key Results: A total of 103,048 patients from 15 studies were included. The combined results suggest that MetS is a risk factor of GERD (OR: 1.66, 95%CI: 1.38–1.99). Among the individual metabolic components, abdominal obesity (OR: 1.42, 95%CI: 1.22–1.64), hypertriglyceridemia (OR: 1.50, 95%CI: 1.27–1.78), hyperglycemia (OR: 1.31, 95%CI: 1.07–1.61), and hypertension (OR: 1.19, 95%CI: 1.07–1.33) are risk factors of GERD. Conclusions and Inferences: MetS is a risk factor of GERD, and among the abnormal metabolic components that establish the diagnosis of MetS, abdominal obesity, hypertriglyceridemia, hyperglycemia, and hypertension are risk factors of GERD. [ABSTRACT FROM AUTHOR]