Search Results (57)

To circumvent the computational bottlenecks associated with the intermediate steps (e.g., least squares fitting) in conventional sine wave similarity principles and directly acquire the energy metrics required for stabilized sinusoidal waveform characterization, this study leverages time domain probability distribution theory. From a complementary advantage perspective, a novel transformer inrush current identification criterion is developed using the Wasserstein distance metric. The methodology employs feature discretization to extract target/template signals, transforming them into state vectors for sample labelling. By quantifying inter-signal energy distribution disparities through this framework, it achieves a precise waveform similarity assessment in sinusoidal regimes. The theoretical analysis and simulations demonstrate that the approach eliminates frequency domain computations while maintaining implementation simplicity. Compared with conventional sine wave similarity methods, the solution streamlines protection logic and significantly enhances practical applicability with accelerated response times. Furthermore, tests conducted on field-recorded circuit breaker closing waveforms using MATLAB R2022a confirm the effectiveness of the proposed method in improving transformer protection performance. Full article

Accurately simulating wave breaking is crucial for modeling hydrodynamics over steep coral reef slopes, yet it remains a challenge for Boussinesq-type models like FUNWAVE-TVD. The model’s standard hybrid breaking mechanism, triggered by a fixed free surface elevation-to-depth ratio ($\eta /d>0.8$), often lacks physical sensitivity to local slope and wave conditions prevalent in reef environments and suffers from inaccuracies associated with using η as a direct proxy for wave height (H). This study introduces and validates a novel, enhanced hybrid breaking module within FUNWAVE-TVD, specifically designed to overcome these limitations on steep slopes. The core novelty lies in the synergistic implementation of two key components: (1) replacing the fixed threshold with a dynamic, physically-based criterion derived from the Modified Goda formula (MGO) by Rattanapitikon and Shibayama, which calculates the breaking wave height ($H_b$) based on local depth, slope, and deep-water wavelength; and (2) developing and applying a practical method, using the wave vertical asymmetry relationship proposed by Yu and Li, to dynamically convert the calculated $H_b$ into an equivalent breaking surface elevation threshold (${\eta }_b$). This derived dynamic threshold (${\eta }_b/d$) is then used to trigger the model’s existing switch from Boussinesq to Nonlinear Shallow Water Equations (NSWE), allowing for energy dissipation via shock-capturing while retaining the physical basis of the MGO criterion. The performance of this enhanced module was rigorously evaluated against five laboratory experiments of regular waves breaking on impermeable slopes ranging from mild (1:10) to extremely steep (1:1), contrasting results with the original FUNWAVE-TVD. The modified model demonstrates significantly improved accuracy (model skill increases ranging from 10.16% to 42.49%) compared to the original model for breaking location and wave height prediction on steeper slopes ($m\ge 1:6$). Conversely, tests on the 1:1 slope confirmed the inherent limitations of the MGO criterion itself under surging breaker conditions ($m\ge 1:2.3$), highlighting the applicability range. This work provides a validated methodology for incorporating slope-aware, dynamic breaking criteria effectively into hybrid Boussinesq models, offering a more robust tool for simulating wave processes on steep reef topographies. Full article

This study investigates the seabed response induced by wave shoaling and breaking on a sloping seabed through numerical modeling. A coupled approach is employed, integrating a Reynolds-Averaged Navier–Stokes (RANS) wave model with a poro-elastic soil model based on Biot’s consolidation theory. The wave model incorporates a stress-$\omega$ turbulence model to mitigate the tendency to overestimate turbulence intensity during wave breaking. The numerical simulations capture key hydrodynamic processes such as wave transformation, breaking-induced turbulence, and the evolution of pore pressure and soil stress within the seabed. Model validation against analytical solutions and experimental data confirms the reliability of the numerical framework. The study simulates two types of breaking waves: spilling and plunging breakers. The results indicate that wave breaking significantly alters the spatial and temporal distribution of pore pressures and effective stresses in the seabed. In particular, the undertow generated by breaking waves plays an important role in modulating seabed responses by inducing asymmetric pore pressure and stress distributions. The influence of soil permeability and the degree of saturation on wave-induced responses is investigated, showing that higher permeability facilitates deeper pore pressure penetration, while under lower permeability conditions, a higher degree of saturation significantly enhances pore pressure transmission. Additionally, different breaker types exhibit distinct seabed response characteristics, with plunging breakers causing stronger nonlinear effects. These findings provide valuable insights for the design and stability assessment of marine and coastal infrastructure subjected to dynamic wave loading. Full article

The breaker index in contemporary spectral wave models is a vital parameter in studying depth-induced wave breaking, which is an important mechanism in coastal engineering. In the previous study, the authors modified a Goda type breaker index formula and parameterized it in a spectral wave model. Although this parameterization model can accurately simulate nearshore wave height variations under various laboratory and field conditions, the computation of deep-water wave conditions in the formula necessitates reverse calculation based on the incident waves, thus limiting its applicability. To solve this problem, a new expression for this Goda type breaker index is rederived, enabling its applicability to simulate breaking waves caused by variable wave conditions on open boundaries and wind field inputs in the whole computational region. The model’s capability to simulate wave heights in laboratory and field experiments is comparable to that of the original formula. Full article

Climate change impacts are unpredictable and can change rapidly or over time; anthropogenic stressors work synergistically to strengthen their impact on vulnerable ecosystems including in the fisheries sector. This study focused on understanding and documenting the historical occurrence of extreme climate change impacts as exemplified by super typhoon Pablo (Bopha), which wreaked havoc in Baganga, Davao Oriental, almost a decade ago. A mixed-methods approach was used, using semi-structured interviews (N = 120) and focus group discussions (FGD) with small-scale fishers in the four fishing villages to assess the impacts of climate change and their adaptation after the events occurred. Our findings indicate that the fishing villages were exposed to the same impacts of climate change or the super typhoon which destroyed their lives and livelihoods. Consequently, this affected their catch per trip and fishing operations. Moreover, due to the impact of the super typhoon, fishers in Baganga developed psychological distress and trauma (emotional 44% and physical 24%) due to the extreme event. To survive, their adaptation strategies relied on government and non-government assistance provisions and projects, e.g., planting mangrove trees, construction of a seawall with wave breakers, cash-for-work activities, and tourism, as an alternative livelihood. Moreover, our study revealed that the communities have limited knowledge about the impacts of climate change, the local government lacks clear management goals for fisheries conservation and there was widespread use of illegal fishing gear. There is a strong need to implement rules, policies, and adaptation measures to build more resilient fishing communities. Full article

The global demand for coastal urbanization is rising with the increasing population. Alas, living close to the ocean threatens human endeavors with high currents, waves, and increasing storm frequency. Accordingly, the need for more coastal defense structures (CDSs) rises. Structures built from complex units meant to prevent and/or mitigate coastal erosion and floods, additionally providing wave protection or wave attenuation, are constructed on and near natural habitats where they alter local ecosystems. Traditional CDSs mostly fail to harbor diverse and abundant communities. However, this can be changed by eco-friendly methodologies and designs that are being tested and implemented to improve CDSs’ ecological value. Some of these can be implemented during the construction period, while others can fit on existing structures, such as wave breakers and seawalls. Effective methods include augmenting surface rugosity through strategic perforations, integrating artificial panels for increased complexity, implementing soft (naturally based) engineering solutions such as geotextiles, replacing industrial concrete mixtures for CDS construction with “green concrete” and ecologically friendly mixtures, and using alternative, eco-friendly units in CDS erections. In this mini review, we suggest that by integrating sustainable practices into coastal development, we can significantly mitigate the ecological damage caused by traditional CDSs and promote more harmonious relationships between human construction and the marine environment. This shift towards environmentally conscious coastal defenses is essential and a responsibility for ensuring the long-term sustainability of our coastal communities and the health of our oceans. We present current methodologies used on breakwaters worldwide. Full article

In order to effectively obtain the contact state without disassembling the interrupter chamber of the SF6 circuit breaker, a dynamic capacitance measurement method for the breakout process of the circuit breaker is proposed. The dynamic capacitance measurement is carried out by applying high-frequency excitation at both ends of the interrupter chamber, the dynamic capacitance measurement system that can meet the pF-level variation is designed, and the measurement method for correcting the stray capacitance of the wire is proposed. Based on the fundamental wave component method, a dynamic capacitance calculation method is proposed for the circuit breaker tripping process, and the optimal parameter combination for the dynamic capacitance calculation is determined through simulation analysis. The best combination of computational parameters for dynamic capacitance calculations was determined to be a triangular window, a window length of 480, and an overlap length of 0. The dynamic capacitance-travel curve of SF6 circuit breaker tripping process under different ablation states is obtained in the final test, and the results show that: with the increase in contact ablation, the overall shape of the dynamic capacitance-travel curve is basically unchanged, and the capacitance value at the starting point increases and the travel value decreases, which provides a new idea for the evaluation of circuit breaker interrupter chamber’s electric life. This provides a new idea for the electrical life assessment of circuit breaker interrupters. Full article

The erosion of the seabed in front of shoreline structures due to wave action is a critical concern. While previous models accurately depict fluid and sediment interactions, they each have limitations and require significant computational resources, especially when simulating complex processes. This study proposed and validated a numerical model for simulating wave-induced sediment transport by integrating three key components: (1) a main solver based on large eddy simulation that includes the porosity of permeable materials, (2) a volume of fluid module to track the air–water surface, and (3) a sediment transport module that includes both bedload and suspended load to compute sediment concentrations and seabed changes. The model was validated against previously published experimental data, demonstrating its accuracy in capturing both wave motion and seabed profile changes induced by sediment transport. Furthermore, the numerical model was applied to study the effects of varying breakwater slopes on sediment seabed profile changes. The results show that steeper breaker slopes led to more concentrated wave energy near the structure, resulting in deeper scouring and higher sediment displacement. These results indicate that the proposed model is a valuable tool for coastal engineering applications, particularly for designing breakwaters, to mitigate sediment erosion and improve sediment stability. Full article

Flow ultrasound generators are devices that emit high-frequency sound waves due to the hydrodynamic instability of the supersonic flow. In the electric power industry, such generators are used in arc quenching systems of high-voltage gas blast circuit breakers. The design of the flow ultrasound generator includes a nozzle and a hollow cylindrical resonator. Self-oscillations of the sealing waves occur when a supersonic gas jet collides with a resonator. This article is devoted to the analysis of the arrester operation, which has design features of flow ultrasound generators. The paper includes both experimental investigations of the proposed spark gap arrester design and mathematical modeling of the processes occurring in it. A description of the methods used is presented, and a comparison of the time dependences of currents and voltages obtained as a result of experimental studies and as a result of calculations is performed in the next section. The calculation results include oscillograms of the voltage and current, and the plasma temperature distribution in the arrester chamber at different moments of time. The investigations show that the presence of a nozzle and resonator leads to an intensification of the gas dynamic effect on the electric arc. Full article

Due to the demand for temporary rapid grid connection in renewable energy power plants, the topology structure of T-connected power lines has been widely used in the power grid. In this three-terminal system, fault localization is difficult because of traditional impedance-based or traveling wave-based fault localization methods; the three-terminal data should be synchronized and communicated. Since different terminal assets belong to different enterprises, it is actually difficult to maintain good synchronization between them. Therefore, in practical applications, the fault location of T-connected power lines often fails. This article proposes a single terminal fault location method for a T-connection power line to address this issue. It is based on the fact that the local topology of the T-connected power line in the healthy phase remains unchanged during the fault-clearing process. It utilizes the sequential current and voltage data changes generated by the sequential tripping ping emitted by the circuit breaker from different terminals to describe the constant topology of the healthy phase as an equation and calculates the accurate fault location after solving the equation. The Levenberg–Marquardt algorithm was used to calculate fault distance and transition resistance, and the effectiveness of this method was verified through simulation. Full article

An analysis of the interactions between wave-induced velocities and seagrass meadows has been conducted based on the large-scale CIEM wave flume data. Incident irregular wave trains act on an initial 1:15 sand beach profile with measurement stations from the offshore of a surrogate meadow until the outer breaking zone, after crossing the seagrass meadow. The analysis considers variability and peaks of velocities, together with their skewness and asymmetry, to determine the effects of the seagrass meadow on the near bed sediment transport. Velocity variability was characterized by the standard deviation, and the greatest changes were found in the area right behind the meadow. In this zone, the negative peak velocities decreased by up to 20.3%, and the positive peak velocities increased by up to 11.7%. For more onshore positions, the negative and positive peak velocities similarly decreased and increased in most of the studied stations. A progressive increase in skewness as the waves passed through the meadow, together with a slight decrease in asymmetry, was observed and associated with the meadow effect. Moving shoreward along the profile, the values of skewness and asymmetry increased progressively relative to the position of the main sandbar. The megaripple-like bedforms appeared earlier when the meadow was present due to the higher skewness, showing a belated development in the layout without the meadow, when skewness increased further offshore due to the proximity of the breaker sandbar. To assess the sediment transport capacity of a submerged meadow, the SANTOSS formula was applied, showing that in front of the meadow, there was a higher sediment transport capacity, whereas behind the meadow, that capacity could be reduced by up to 41.3%. In addition, this formula was able to produce a suitable estimate of sediment transport across the profile, although it could not properly estimate the sediment volumes associated with the bedforms generated in the profile. Full article

Circuit breakers, affected by multiple lightning strikes after the breaker has been tripped, can break down again, which will reduce the life of the circuit breaker and threaten the stable operation of the power system. Aiming at this problem, this research obtained the temperature diffusion process of the inrush current process of the circuit breaker’s opening and breaking, using the Schlieren technique combined with existing image recognition technology to obtain the temperature characteristics of the airflow in the air gap of the contact, as well as the characteristics of the flow of air itself. The results of the study show that the circuit breaker breakdown process generates a shock wave with a velocity approximately equal to the speed of sound under the same conditions. The maximum velocity of the airflow boundary diffusion is about one-quarter of the speed of sound under the same condition, and it decays very fast, reducing to the airflow drift velocity within 10 ms after breakdown. The maximum temperature of the thermals is concentrated between 6000 K and 8000 K, and the temperature change is approximately inversely proportional to the square of the time. This research provides the basis for the design of a circuit breaker’s contact structure, opening speed optimization method, interrupter chamber, and insulation design optimization. Full article

Microplastics, ubiquitous in our environment, are significantly impacted by the hydrodynamic conditions around them. This study utilizes CFD to explore how various breaker types influence the dispersion and accumulation of microplastics in nearshore areas. A special focus is given to the impact of wave dynamics and particle size, particularly on buoyant microplastics in spilling breakers. It was discovered that spilling breakers, common on gently sloping seabeds, encourage broad dispersion of microplastics, notably for smaller-sized particles. Plunging breakers exhibit a similar pattern but with less dispersion and an initial forward movement of neutral and heavy particles. Surging breakers feature minimal dispersion and a distinct oscillatory motion. It has been observed that medium-sized particles with a 1 mm diameter in this work exhibit the most substantial forward movement, likely due to an optimal balance between inertia and viscosity, enabling an effective response to wave momentum. Larger particles, influenced mainly by inertia, tend to show less dispersion and advection. Meanwhile, smaller particles, more affected by viscosity, demonstrate greater dispersion, interacting extensively with wave-induced turbulence. This study reveals the significance of inertia in the behavior of microplastics over slopes, emphasizing the importance of considering inertial effects for precise modeling of microplastic movement in nearshore areas. Full article

Floating breakwaters have recently been generating increasing interest as a vital means to provide shelter and protect the ever-increasing number of structures deployed at sea. Notwithstanding the novel ideas being put forward, to date, floating breakwater deployment has been limited to inshore and shallow water areas. The scale of such structures has been restricted to the smaller spectrum. Furthermore, whilst some concepts to integrate floating breakwaters with other offshore systems have been proposed to benefit from cost-sharing strategies, studies related to floating breakwaters integrating energy storage are lacking in the open literature. The present research investigates the wave attenuating and dynamic performance of a large-scale floating breakwater in deep seas with a hydro-pneumatic energy storage system also integrated within the structure. This article highlights the arising need for floating breakwaters and sheds light on the present-day technological status of floating wave breakers. It then lays the ground for the proposed, novel floating breakwater concept that aims to address the current knowledge gaps in this field of study. The simulation results generated from numerical modelling via the potential flow solver ANSYS^® AQWA™ have been promising, connoting that the addition of hydro-pneumatic energy storage to a floating breakwater will not lead to a degradation in the dynamic performance or wave breaking efficiency of the floating structure. Full article

Grid-connected photovoltaic (PV) power systems are one of the most promising technologies to address growing energy demand and ecological challenges. This paper proposes smart switching to mitigate inrush currents during the connection of single-phase transformers used in PV systems. An effective inrush current mitigation contributes to the reliability of PV systems. The inrush current severity is influenced by the pseudorandom residual flux at the transformer core and the energization point-on-wave. The most common approach to avoid inrush currents is controlled connection, which requires prior knowledge of the residual flux. However, the residual flux can differ in each case, and its measurement or estimation can be impractical. The proposed smart switching is based on a comprehensive analysis of the residual flux and the de-energization trajectories, and only requires two pieces of data (ϕ_RM and ϕ₀, flux values of the static and dynamic loops when the respective currents are null), calculated from two simple no-load tests. It has a clear advantage over common approaches: no need to estimate or measure the residual flux before each connection, avoiding the need for expensive equipment or complex setups. Smart switching can be easily implemented in practical settings, as it considers different circuit breakers with distinctive aperture features, making it cost-effective for PV systems. Full article