Current Issue : October-December Volume : 2026 Issue Number : 4 Articles : 5 Articles
The interaction between wind turbines can cause energy losses, which need to be accurately modeled in order to design energy efficient wind farms. A steady-state Computational Fluid Dynamics (CFD) method can be employed to take into account the mean atmospheric effects on the turbine interaction. However, such a method can suffer from spurious numerical waves when a shallow atmospheric boundary layer (ABL) height relative to turbine tip height is employed, which compromises confidence in the results. In this work, we show that the numerical waves can be removed by excluding Coriolis-induced wind veer through a novel steady-state inflow model of the ABL, for an ABL height that is twice the size of the turbine tip height. The inflow model is shown to be in balance with a large empty successor domain and can therefore be used to isolate the effect of wind veer on the wind farm. When the ABL height is lowered to the turbine tip height small scale numerical waves can reappear, which shows that the wind veer is not the only source of the numerical waves. Wind farm simulations with a laminar version of the ABL inflow model, with and without veer, indicate that the presence of a low (eddy) viscosity can cause numerical instabilities. More research is required to further investigate the origin of the numerical waves and how to remove them in order to perform robust steady-state CFD simulations of wind farms with large wind turbines subjected to shallow ABLs....
Synchronous machines used in wind turbines typically use rare earth permanent magnets (PMs) due to the possibility of high power densities and efficiencies. However, alternative non-PM topologies are gaining popularity due to the cost and supply volatility of PMs. Wound-field flux-switching machines (WFFSMs), although boasting high torque densities and being PM-free, have lower power densities than PM machines. However, a doublestator wound-field flux-switching machine (DSWFFSM) exemplifies even greater power density. This study investigates the application of DSWFFSMs for direct-drive wind applications. Furthermore, the performance of an optimized 3 MW DSWFFSM design is compared with a single-stator WFFSM design. Both designs are based on the volume of a single-stator PM flux-switching machine from the literature. Although the torque per weight for the DSWFFSM and the single-stator WFFSM are similar, the torque per volume for the DSWFFSM is shown to be significantly exceptional. The torque ripple in the DSWFFSM is also smaller, but the efficiency is slightly lower than the single-stator WFFSM. The DSWFFSM design, which is shown to be comparable to PM-based topologies in terms of power density, highlights a low-cost, sustainable, clean energy generator topology....
Ocean wind waves are a fundamental manifestation of complex dynamics in geophysical fluid systems, characterized by a rich interplay between dispersion and nonlinearity. While linear wave theory provides a first-order description of wave motion, real-world oceanic environments are governed by nonlinear interactions that are responsible for the transfer of energy between waves of different lengths. Established theoretical concepts predict that four-wave resonant interactions serve as the primary mechanism for energy transfers among wave components in oceanic surface wave fields. Although the presence and efficiency of these resonant interactions have been demonstrated in controlled wave tank experiments, their direct identification in the real ocean, where a large number of random waves interact, has remained elusive. Here, using a stereoscopic system that enables the measurement of surface elevation in both space and time, we provide experimental evidence of resonant interactions in ocean wind waves. Our data not only reproduce the well-known figure-eight pattern predicted by Phillips but also reveals a continuum of different resonant configurations that closely match the theoretical predictions. These findings support the validity of third-generation ocean wave models, strengthening their ability to accurately capture wave dynamics in the ocean....
Large-eddy simulations (LES) are performed to examine the effects of a monochromatic wave field on the flow and power output of an inline offshore wind turbine array. The air–sea interaction is modeled using a one-way coupling framework implemented through a hybrid immersed-boundary/level-set method. The water-side velocity field is prescribed using the solution of linear wave theory. The airflow field responds dynamically to the evolving sea-surface elevation, which is tracked via the level-set equation. By varying wind–wave alignment (aligned vs. opposing) and wave age (young waves to old waves), the influence of different sea states on the array performance are investigated. Our findings show that the presence of surface waves modifies the mean flow and wake recovery within the array. Wind-opposing wave conditions lead to enhanced momentum transport and increased Reynolds shear stresses in the wake of the wind turbines. This momentum redistribution promotes faster wake recovery compared to both wind-aligned wave cases and the baseline onshore scenario. Elevated power fluctuations compared to the baseline case are found when wind and waves are opposing. Relative to the baseline case, the mean power production of the array increases by 2.6% and 6% for wind–wave aligned and wind–wave opposing conditions, respectively, for the wave ages considered in this work. Overall, the findings highlight the impact of wave-induced turbulence modulation and wake dynamics on offshore wind farm performance....
1. Wind is a major factor driving seabird movement and energetics, the effects of which are modulated by morphology. Developments in tagging technology now make it possible to test predictions from aerodynamic theory about the effects of wind on flight performance in free-ranging birds. Waves are also thought to have a strong influence on seabird movement but have received less attention. 2. We investigated the interplay between wind, waves, and morphology and tested predictions of flight theory in giant petrels (Macronectes spp.), which show greater sexual size dimorphism than any other seabird. We quantified flapping rates as a proxy of energy expenditure using accelerometers deployed on northern giant petrels (M. halli; n = 45) and southern giant petrels (M. giganteus; n = 48) breeding at Bird Island, South Georgia in 2022 and 2023. Wind and waves experienced by birds tracked with Global Positioning System (GPS) loggers were integrated with ERA5 reanalysis data to assess how flapping rates and ground speeds, respectively, were influenced by wind and waves. Using generalized additive mixed models, we predicted the spatial distribution of suitable habitat for soaring based on wind and wave conditions. 3. Both wind and waves strongly influenced flight energetics; flapping rates decreased with increasing wind speed and swell height in all species and sexes. Together, wind and waves allowed giant petrels to reduce flapping rates by 76% to 91%. Wind also influenced the speed of travel; ground speed increased with wind speed in tail-and crosswinds, but generally decreased with wind speed in headwinds. 4. Male giant petrels had higher wing loadings, and as predicted by flight theory, required higher air speeds for soaring flight and had higher flapping rates than females. Potential soaring habitat was much more limited for male than for female giant petrels, suggesting that differences in flight energetics between sexes may contribute to sexual segregation in foraging areas. 5. Our results demonstrate how morphology, wind and waves combine to influence the flight energetics of giant petrels. Understanding the interactions among these factors is central to understanding environmental drivers of seabird distribution and to predicting responses to continued climate change....
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