Search Results (1,339)

This study presents a full-scale steady CFD methodology for evaluating flow quality in a large-scale low-speed wind tunnel (8 m × 6 m test section, 130 m/s). The tunnel geometry is resolved at 1:1 scale, the damping screens and honeycomb are modeled as porous media, and results are validated against wind tunnel test data and the GJB 1179A-2012 acceptance criteria. The baseline configuration reproduces the axial static pressure gradient within the acceptance criterion but substantially overpredicts turbulence intensity, dynamic pressure coefficient, and both velocity direction deviation angles. Damping screens, modeled as porous jumps, provide the dominant correction, bringing all metrics within the acceptance limits. Adding honeycomb yields incremental improvement: porous zone modeling preserves or improves all metrics, whereas a porous jump representation pushes velocity direction deviations beyond the limit. Between RNG k-ε and SST k-ω, only turbulence intensity is closure-dependent, with RNG k-ε closer to experiment. At Ma ≈ 0.38, compressibility does not alter the flow quality assessment, confirming that incompressible assumption is sufficient. By replacing costly physical trials with a validated CFD workflow, these findings provide a practical, resource-efficient reference for the CFD-based evaluation, design, and retrofit of wind tunnel infrastructure that underpins renewable-energy and energy-efficiency research. Full article

Tension-leg platform (TLP) horizontal-axis wind turbines (TLP-HAWTs) have become increasingly important in deep-water offshore wind energy development. However, their performance is strongly affected by coupled platform motions induced by wind and wave loads, making fully coupled simulations a critical prerequisite for accurate performance assessment. Conventional fully coupled approaches often struggle to balance computational efficiency and numerical fidelity. In this study, a simplified sequential coupled modeling framework is proposed based on the commercial solvers OrcaFlex and STAR-CCM+. In this framework, OrcaFlex is employed to simulate the hydrodynamic response of the floating platform, and the resulting platform motions are subsequently imposed as prescribed inputs in high-fidelity CFD-based aerodynamic simulations. Based on the proposed framework, a series of case studies of a 15 MW TLP-HAWT are conducted to investigate the effects of wind-induced and wave-induced platform motions on aerodynamic performance. The results indicate that wind-induced platform motions have a negligible impact on local inflow conditions and vortex intensity, and their influence on mean blade loads and wake topology can be safely ignored under rated conditions. In contrast, wave-induced motions significantly enhance unsteady aerodynamic loads, intensify vortex shedding, alter torque distribution along the blades, and increase wake turbulence intensity as well as velocity deficit. These findings suggest that wave-induced platform dynamics dominate the unsteady aerodynamic response and wake evolution of TLP-HAWTs under rated conditions, while wind-induced motions play a secondary role. The results provide valuable insights for reduced-order modeling, control strategy development, and the design optimization of efficient floating offshore wind turbines. Full article

The wake effect inside wind farms reduces the inflow wind speed and increases the turbulence intensity of downstream turbines, resulting in power loss and increased fatigue loads. Active yaw control can mitigate wake interference through collaborative optimization of turbine yaw angles. However, most existing methods rely on steady-state wake models, which fail to capture the dynamic delay characteristics of wakes and usually lead to excessive yaw actuation losses. To address these issues, this paper constructs a dynamic wake model suitable for real-time control based on the OFF dynamic wake framework (OnWARDS, FLORIDyn, and FLORIS), adopting an improved three-dimensional analytical wake model at the lowest level. On this basis, a finite control set model predictive control (MPC) active yaw controller is designed. Aiming to maximize power generation and minimize yaw loss, the controller realizes rolling optimization of yaw actions combined with ARIMA-based wind direction prediction and particle swarm optimization. Simulations on the 4 × 4 turbine array of the Horns Rev I wind farm show that the proposed method increases the total power by 2.25%, which is 0.79% higher than that obtained by the deadband controller. It results in lower power loss for upstream turbines and higher power gain for downstream turbines, reduces the total yaw travel by nearly 1000° compared with the deadband controller, and produces smaller power fluctuations under sharply changing wind directions. Full article

This paper investigates the influence of coarse particle size on pressure characteristics through horizontal pipe transportation experiments of coarse particles and sand-laden water. As particle size increases, the thin and long grain accumulation layer forming at the pipe bottom and particle clusters above the layer vanish, most grains roll and bounce more quickly, the instantaneous pressure fluctuation intensity increases exponentially, and the time-averaged pressure decreases linearly along the flow direction. The fluctuating pressure probability density tends to obey a Gaussian distribution, and the turbulence power below 16 Hz increases. After adding fine sand constituting sand-laden water flows, the instantaneous pressure fluctuation intensity, transportation energy loss speed and fluctuating pressure amplitudes increase. With increasing particle size, the fitted Gaussian distribution of the fluctuating pressure probability density changes from thin to short and wide, and the spectral power of the measured pressure fluctuations increases within the resolvable frequency range, especially in the range from 8 to 10 Hz. Full article

Static wake steering can increase wind-farm power production, but its application to floating offshore wind farms requires assessment of the coupled wake, platform, structural, and station-keeping response. This study evaluates whether power-maximizing static yaw setpoints identified using the steady, control-oriented FLORIS model retain their benefit when transferred without re-optimization to a coupled FAST.Farm floating wind-farm model. The reference farm comprises four IEA Wind 15 MW turbines mounted on VolturnUS-S semi-submersible platforms. Greedy and static wake-steering operations are compared at three below-rated wind speeds, three sea states, and five matched turbulent-inflow realizations, resulting in 90 farm-level FAST.Farm simulations. Wake behavior is characterized through wake-center deflection, meandering, and velocity-deficit profiles, while turbine and mooring fatigue responses are evaluated using paired damage-equivalent-load statistics. Static wake steering increases mean farm power under all nine investigated wind–wave conditions. The gains are approximately 5.1–$5.2\%$ at $7\mathrm{m}{\mathrm{s}}^{-1}$, $5.0$–$5.1\%$ at $8\mathrm{m}{\mathrm{s}}^{-1}$, and $4.0$–$4.2\%$ at $9\mathrm{m}{\mathrm{s}}^{-1}$, with all paired $95\%$ confidence intervals remaining above zero. The gain results from a power redistribution in which the intentionally yawed upstream turbine incurs a local loss that is exceeded by the combined recovery of the downstream turbines. The fatigue response is strongly component- and turbine-dependent. The paired farm-mean blade-root DEL decreases by $0.82$–$2.24\%$, whereas the tower-base DEL increases by $0.76$–$2.78\%$, and the FairTen1 response generally increases by $0.88$–$2.92\%$. The farm-mean yaw-bearing response is mixed, ranging from a $1.15\%$ reduction to a $4.32\%$ increase. Turbine-level analysis reveals larger localized penalties, reaching approximately $10.4\%$ for the yaw-bearing DEL and $12.8\%$ for FairTen1. Spectral analysis associates the yaw-bearing response with yaw-induced aerodynamic and structural excitation, while the tower-base response is strongly influenced by low-frequency wave–platform dynamics. A complementary FLORIS sensitivity analysis demonstrates that the optimized aerodynamic benefit depends strongly on wind direction, spacing, wind speed, and turbulence intensity. For a Tampen-derived 11-turbine layout, resource weighting over the modeled 4–$13\mathrm{m}{\mathrm{s}}^{-1}$ interval produces an annual energy-contribution increase of $3.653\mathrm{GWh}{\mathrm{year}}^{-1}$, or $0.921\%$. These results provide numerical evidence that static wake steering can retain a positive power benefit in a coupled floating wind-farm environment, but controller assessment must include turbine- and component-specific dynamic loads rather than farm power alone. Full article

To investigate the influence of inlet structure optimization on pressure pulsation and energy transport characteristics in mixed-flow pumps, this study employed experimental and numerical calculation methods to analyze both original and optimized models. The SST-SAS turbulence model was selected for flow field computation. The experimental and numerical results showed that inlet optimization increased the head at the design condition by 1.52 m, improved the efficiency by 5.38%, and reduced the pressure pulsation amplitude by more than 90%. Analysis of energy transport term distribution characteristics within the pump revealed the mechanism behind pulsation intensity improvement: the pressure propulsion power distribution in the impeller became more stable, while the Lamb vector divergence dissipation regions and enstrophy dissipation regions substantially decreased, thereby increasing the proportion of pressure propulsion power contribution. The enhanced energy transport characteristics and improved flow field stability in the impeller region collectively optimized energy conversion performance within the impeller. Full article

To address the challenges of adsorption instability and obstacle-crossing difficulties faced by wall-climbing robots in the harsh operation and maintenance (O&M) environment of offshore wind turbine (OWT) towers, this paper presents the design of a magnetic-adhesive wall-climbing robot with a planetary-gear configuration and investigates its wind resistance stability. First, the magnetic circuit layout is optimized through finite element analysis, revealing that the F-16 continuous planetary configuration (16 poles) effectively suppresses magnetic flux leakage and forms an integrated magnetic pad, maintaining adsorption force at a large air gap of 20 mm, thereby enhancing magnetic robustness during obstacle crossing and making it the optimal choice for high-load offshore conditions. Second, an unsteady flow field model based on the Kaimal turbulence spectrum is constructed to analyze aerodynamic loads. Fluid–structure interaction (FSI) simulations demonstrate that at a height of 30 m, the turbulence integral scale matches the robot dimensions, and combined with the Venturi effect of gap jet flow, this leads to peak turbulence intensity and pitching moment, creating a hazardous, pronounced aerodynamic amplification condition. Finally, an anti-slip stability model is established, revealing that vertical wall climbing represents the critical loading scenario; the magnetic adhesion system must deliver a total adsorption force of no less than 1000 N to resist a 35 m/s wind speed under low-friction conditions, providing a quantitative design basis for anti-wind safety. This study integrates magnetic circuit optimization, turbulence-resolved aerodynamics, and macroscopic anti-slip mechanics, offering theoretical support and engineering guidance for the safe deployment of intelligent O&M equipment for offshore wind power. Bench-scale measurements of magnetic adhesion force, friction coefficient, and translation force fluctuation support the exponential-decay magnetic model and the multi-wheel phase-interleaving concept; however, the current 4 × 16-pole prototype delivers ~627 N at the 2 mm working gap, below the 1000 N design target. The design methodology is therefore validated, while the current physical configuration requires further iteration of the working gap or magnet grade before it can be considered operationally adequate. Full article

Propulsors are essential power units for underwater vehicles and major sources of self-noise, with unsteady pressure pulsations linked to flow-induced noise. To study the impact of guide vane case on the hydrodynamic performance and pressure pulsation of a shaftless pump-jet thruster, six guide vane configurations were first compared under a reference operating condition of 600 rpm: a vaneless baseline, fixed vertical guide vanes, fixed forward-inclined guide vanes, fixed reverse-inclined guide vanes, co-rotating guide vanes, and counter-rotating guide vanes. Based on this comparison, the vertical-vane and counter-rotating-vane configurations were selected for extended operating-condition analysis under three rotational speeds and three inflow conditions. Transient numerical simulations were conducted using the SST $k-\omega$ turbulence model. The rotating regions were defined in a rotating reference frame, and the unsteady rotor–stator interaction was resolved using a transient sliding-mesh interface. Results show that the counter-rotating guide vane configuration achieves the highest head and efficiency among the tested cases, with a head of 1.8955 m and efficiency of 0.7306, representing increases of 19.64% and 22.87% over the fixed vertical guide vane case. The fixed forward-inclined guide vane exhibits the strongest thrust fluctuation and pressure pulsation. Pressure-pulsation intensity generally decreases from the impeller rim toward the central axis. Frequency-domain results indicate that most cases are dominated by the blade-passing frequency, whereas the counter-rotating guide vanes show a response nearly twice this frequency. Full article

Accurate detection of atmospheric turbulence intensity is essential for atmospheric optics and laser communication, yet efficient inversion methods remain insufficient. This work explores the feasibility of utilizing Gaussian beams and Gaussian Vortex beams for the inversion of atmospheric turbulence intensity (C_n²). We constructed an SLM-based turbulence simulation platform to generate phase screens with different turbulence intensities and acquire corresponding beam spot datasets. A ConvNeXt-based convolutional neural network is optimized, and its performance is compared with the traditional beam average width fitting method. Furthermore, a novel fusion inversion model is proposed by integrating beam average width parameters and beam spot feature information. Experimental results indicate that, for nine refined C_n² turbulence grades, the optimized CNN achieves an inversion accuracy of 98%, while the beam average width method obtains 84.56% based on Gaussian Vortex beams. In contrast, the corresponding accuracies decreased to 95% and 73.84% when adopting conventional Gaussian beams. Compared with the standalone CNN model, the proposed fusion model achieves absolute accuracy improvements of 7.0% in indoor experiments and 2.0% in outdoor field tests. The results demonstrate that Gaussian Vortex beams combined with beam average width features exhibit superior performance in C_n² inversion. The proposed fusion model presents reliable and promising inversion capability, which provides a feasible technical solution for the design and optimization of atmospheric turbulence monitoring systems. Full article

The accuracy of the numerical simulation of unsteady cloud cavitation around a hydrofoil depends on the combination of the cavitation model, the Reynolds-Averaged Navier–Stokes (RANS) turbulence model and the exponential coefficient n of the Reboud’s correction. To assess the influence of such choices, three turbulence models, three cavitation models and two values of n have been combined to predict the shedding frequency and the morphology of cloud cavitation around the NACA65012 and NACA0009 hydrofoils. The comparison with analogous experimental results obtained in a cavitation tunnel indicates, firstly, that the same numerical set-up differs in accuracy depending on the hydrofoil geometry. Secondly, within the scope of the two tested hydrofoils and corresponding flow conditions, the Shear Stress Transport (SST) turbulence model and the value of n = 10 appear to be more accurate and more robust for all tested cases. And finally, the predicted shedding frequency is more sensitive to the selection of the turbulence model than to the cavitation model. If an erosion model is implemented, then it is found that the predicted potential energy distribution of the cavitating flow is sensitive to the selected cavitation model. In our case, the Sauer model gives a more accurate distribution and intensity of erosion power than the rest of the cavitation models. Full article

Special orthogonal lateral-intake pumping stations on coastal plains face severe lateral deflection and recirculation in the approach channel and forebay. Their underlying evolutionary mechanisms remain unclear, and conventional rectification methods cause substantial hydraulic losses. Using numerical simulations and hydraulic model experiments, this study investigates these unfavorable flow patterns and proposes an original Combined Arc-Frame Flow Straightening Structure (CAFS). This newly proposed CAFS differs from existing structures, achieving effective flow pattern improvement with reduced hydraulic loss. Results reveal three typical flow regimes—S-shaped mainstream, branching flow, and recirculation—and the flow field is partitioned into four hydrodynamic zones: the Mainstream Incident Zone, Mainstream Impact Zone, Mainstream Reflection Zone, and Low-Velocity Recirculation Zone. Axial velocity uniformity and flow angle are strongly influenced by lateral velocity, while turbulent kinetic energy exhibits intrinsic correlations with vertical vorticity. Lateral velocity, recirculation intensity, and hydraulic losses all increase positively with the Froude number. The CAFS effectively suppresses the low-velocity recirculation zone. Quantitative data show an improvement of 46.40 percentage points in uniformity of axial velocity distribution, a reduction of 0.157 rad (9°) in velocity-weighted average angle, 60.98% less turbulent dissipation, and 38.85% less total hydraulic loss. This study clarifies lateral-intake defect mechanisms and provides a valuable engineering reference. Full article

This study employs numerical simulations to systematically investigate the combustion characteristics of methane/ethanol blended fuel–air mixtures under non-premixed turbulent conditions. The effects of the methane blending ratio on the flow-field structure, flame morphology, NO emissions, and combustion efficiency are analyzed. The results show that, with increasing methane blending ratio, the recirculation mechanism gradually shifts from near-field local entrainment to far-field transport, accompanied by a reduction in local shear intensity. Methane addition enhances flame intensity, accelerates combustion, shortens flame length, mitigates heat transfer limitations, and reduces combustion delay. At the initial 10% and the final 20% of the methane blending range, the combustion process exhibits pronounced instability. Methane addition significantly suppresses NO formation, with temperature being the dominant controlling factor, while fuel composition also plays an important role. The overall combustion efficiency is improved. However, a slight decrease is observed at low blending ratios (0–0.1), and the enhancement becomes marginal when the methane blending ratio exceeds 0.6. Full article

In the context of economic turbulence, pursuing new development opportunities through digital transformation has become an inevitable choice for Chinese firms, with top executives serving as core decision-makers. Drawing on resource orchestration theory and the too-much-of-a-good-thing effect, this study examines the relationship between executive psychological resilience and enterprise digital transformation, as well as its boundary conditions, using panel data from Chinese A-share listed firms from 2011 to 2024. The results provide evidence of an inverted U-shaped relationship between executive psychological resilience and enterprise digital transformation, suggesting that an optimal level of psychological resilience exists for digital transformation. Beyond this level, manifestations of bounded rationality, including an underestimation of transformation risks and attentional biases, lead to inefficient resource orchestration. Industry capital intensity weakens this nonlinear relationship, while slack resources appear to shift the turning point to an earlier stage. By questioning the cognitive inertia that treats resilience as a universally beneficial personality trait, this study shifts the perspective on the relationship between executive psychological resilience and enterprise digital transformation from a linear to a nonlinear framework. It further extends the application of the resource orchestration theory in the digital transformation context and contributes to research on the micro-level drivers of digital transformation—specifically executive psychological traits. Full article

Physical control technology as an alternative to chemical pesticides is of great significance for modern sustainable agriculture. However, small pests such as tea green leafhoppers and tea thrips possess sensitive aerodynamic receptors that easily perceive disturbances generated by suction airflow and initiate stress-induced escape behavior. The current bottleneck in the state of the art is that conventional straight tube capture devices generate severe airflow pulsations and turbulence near the intake which act as alarm signals causing pests to escape before entering the effective capture zone. To resolve this trade-off, this study developed and validated a variable cross-section wind-suction channel based on the principle of biological behavioral suppression. This design incorporates a three-stage functional structure consisting of a flow-stabilizing intake section a guided acceleration section and a high negative-pressure throat to achieve a synergistic balance between low disturbance induction and strong aerodynamic confinement. Numerical simulations and prototype experiments show that this design establishes a stable rectified environment at the intake with relative wind speed deviations within 5%. Under controlled laboratory conditions, the average capture rate for target pests exceeded 85% within an effective operating radius of 20 cm. Comparative biological validation further confirms that the capture efficiency of this design is improved by more than 32 percentage points compared with a conventional straight-tube benchmark device. Furthermore, the critical stress-response distance was reduced by approximately 50%, significantly enhancing the concealment of the capture process. These findings elucidate the critical role of channel geometry in resolving the conflict between suction intensity and environmental disturbance providing a theoretical foundation and technical support for the development of high efficiency and precision plant protection equipment. Full article

Wave-in-deck slamming generates highly transient impact loads on coastal and offshore deck structures, while the hydrodynamic processes involving air entrapment and its effect on slamming pressures are not fully understood. In this study, regular-wave impacts on a rigid horizontal deck are experimentally investigated using complementary Particle Image Velocimetry (PIV) and Bubble Image Velocimetry (BIV) measurements to systematically examine the evolution of pressure response, flow dynamics (including velocity, vorticity, and turbulence intensity), and entrapped air-cavity dynamics throughout the impact, oscillation, and suction stages. The results show that during the impact stage, the primary pressure peak is generated by rapid upward momentum transfer beneath the deck, while its magnitude and spatial distribution are strongly influenced by the incident wave height and wave period. During the oscillation stage, repeated compression and expansion of the entrapped air cavity influence the post-impact pressure oscillations through continuous redistribution of the surrounding flow. During the suction stage, gravity-driven water withdrawal and progressive flow separation beneath the deck generate a sustained negative-pressure response. The combined pressure, PIV, and BIV measurements provide an experimental framework for characterizing the relationship between flow evolution, cavity dynamics, and pressure response during aerated wave-in-deck slamming. Full article