A Numerical Method for the Dynamics Analysis of Blade Fracture Faults in Wind Turbines Using Geometrically Exact Beam Theory and Its Validation

In pursuit of China’s goals for carbon peak and carbon neutrality, wind turbines are continually evolving to achieve a lower levelized cost of energy. The primary technological focus in the wind power industry is on large-scale, lightweight designs for entire turbines to enhance cost competitiveness. However, this advancement has led to an increased risk of blade fractures under extreme operating conditions. This paper addresses this challenging issue by using geometrically exact beam theory to develop a nonlinear simulation model for long, flexible blades. The model accounts for sudden changes in blade properties at the moment of failure, covering both the extensive motions and deformations of the fractured blade. The validation of the proposed model is carried out by comparing the results from power production cases with bladed simulations and further validating the simulations of blade fracture load cases against measurement data. The methodologies and findings presented in this study offer valuable insights for diagnosing faults in wind turbines

Study on flow field and aerodynamic forces of straight-bladed vertical axis wind turbine

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Effect of Blade Pitch Angle on the Aerodynamic Characteristics of a Straight-bladed Vertical Axis Wind Turbine Based on Experiments and Simulations

The blade pitch angle has a significant influence on the aerodynamic characteristics of horizontal axis wind turbines. However, few research results have revealed its impact on the straight-bladed vertical axis wind turbine (Sb-VAWT). In this paper, wind tunnel experiments and CFD simulations were performed at the Sb-VAWT to investigate the effect of different blade pitch angles on the pressure distribution on the blade surface, the torque coefficient, and the power coefficient. In this study, the airfoil type was NACA0021 with two blades. The Sb-VAWT had a rotor radius of 1.0 m with a spanwise length of 1.2 m. The simulations were based on the k-ω Shear Stress Transport (SST) turbulence model and the wind tunnel experiments were carried out using a high-speed multiport pressure device. As a result, it was found that the maximum pressure difference on the blade surface was obtained at the blade pitch angle of β = 6° in the upstream region. However, the maximum pressure coefficient was shown at the blade pitch angle of β = 8° in the downstream region. The torque coefficient acting on a single blade reached its maximum value at the blade pitch angle of β = 6°. As the tip speed ratio increased, the power coefficient became higher and reached the optimum level. Subsequently, further increase of the tip speed ratio only led to a quick reversion of the power coefficient. In addition, the results from CFD simulations had also a good agreement with the results from the wind tunnel experiments. As a result, the blade pitch angle did not have a significant influence on the aerodynamic characteristics of the Sb-VAWT

Dynamic Analysis of a Moored Spar Platform in a Uniform Current: Fluid Load Prediction Using a Surrogate Model

A moored spar platform, equipped with various instruments, serves as a crucial tool in hydrological monitoring. However, conducting dynamic analyses of a single spar that endures wind and current requires significant amount of computational time. To address this challenge, this study proposes an efficient surrogate model to represent fluid loads. A database is established to capture the relationship between fluid loads, spar displacements and uniform currents based on a numerical model of the spar. Subsequently, an artificial neural network method is employed to construct the surrogate model. Finally, the surrogate model is integrated with a numerical model of the cable, developed using the lumped mass method, to create a coupled model of the moored spar. The dynamic responses of this coupled model align closely with those obtained from the purely numerical model, demonstrating the efficacy of the surrogate model in capturing fluid loads on the spar. In addition to the surrogate model generation approach, this research provides an efficient method to couple the surrogate model with the numerical model in dynamic analysis of floating systems in uniform currents

Research on A High-Sensitivity Temperature Sensor with Multi-Indicator Based on Nano-Cylinder-Loaded Ring Resonator

Increasing sensor sensitivity and maintaining a large FOM (figure of merit) are challenging to achieve at the same time. Adding grooves and asymmetrical structures to the annular cavity increases sensitivity; however, it usually makes the FOM of the structure decrease. Herein, we propose a MIM (metal-insulator-metal) sensor of a novel structure with nano-cylinders loaded in a ring resonator (NCRR), whose sensitivity can reach as high as 3636.4 nm/RIU (refractive index unit). The FOM is maintained around 2000 in the mid-infrared (MIR) region. We find that grating effects only occur in the ring cavity when the cylinder’s distance is below three times its radius, and it can improve the sensitivity of the proposed structure up to 42.3% without decreasing its FOM. In addition, results suggest that our sensor has excellent resistance to eccentricity, which brings in manufacturing. Furthermore, we investigate the capability of the proposed device as a temperature sensor with ethanol, which exhibits a maximum temperature sensitivity of 1.48 nm/°C. We believe that our research has essential application prospects in miniature integrated sensors, optical switches, splitters, filters, and broadband passers

A Microfluidic Biosensor Based on Magnetic Nanoparticle Separation, Quantum Dots Labeling and MnO2 Nanoflower Amplification for Rapid and Sensitive Detection of Salmonella Typhimurium

Screening of foodborne pathogens is an effective way to prevent microbial food poisoning. A microfluidic biosensor was developed for rapid and sensitive detection of Salmonella Typhimurium using quantum dots (QDs) as fluorescent probes for sensor readout and manganese dioxide nanoflowers (MnO2 NFs) and as QDs nanocarriers for signal amplification. Prior to testing, amino-modified MnO2 nanoflowers (MnO2-NH2 NFs) were conjugated with carboxyl-modified QDs through EDC/NHSS method to form MnO2-QD NFs, and MnO2-QD NFs were functionalized with polyclonal antibodies (pAbs) to form MnO2-QD-pAb NFs. First, the mixture of target Salmonella Typhimurium cells and magnetic nanoparticles (MNPs) modified with monoclonal antibodies (mAbs) was injected with MnO2-QD-pAb NFs into a microfluidic chip to form MNP-bacteria-QD-MnO2 complexes. Then, glutathione (GSH) was injected to dissolve MnO2 on the complexes into Mn2+, resulting in the release of QDs. Finally, fluorescent intensity of the released QDs was measured using the fluorescent detector to determine the amount of Salmonella. A linear relationship between fluorescent intensity and bacterial concentration from 1.0 × 102 to 1.0 × 107 CFU/mL was found with a low detection limit of 43 CFU/mL and mean recovery of 99.7% for Salmonella in spiked chicken meats, indicating the feasibility of this biosensor for practical applications

Vapor Growth and Chemical Delithiation of Stoichiometric LiCoO₂ Crystals

Single crystals of LiCoO₂ have been grown by a vapor transport method at high temperature and normal atmospheric pressure. The plate-like single crystals have large (00<i>l</i>) facets (up to 1 mm²) and thicknesses ranging from 5 to 50 μm. A single-crystal X-ray diffraction study confirmed the trigonal <i>R</i>3̅<i>m</i> space group with lattice parameters <i>a</i> = 2.8150(3) Å and <i>c</i> = 14.0516(6) Å at room temperature. Electrical transport measurements indicated that as-grown crystals are highly insulating, with electrical resistivity in the order of TΩ cm at room temperature. This contrasts with the value of 5 Ω cm previously reported for a flux-grown crystal and suggests that vapor growth crystals may have fewer defects. Li-ion deintercalation of LiCoO₂ crystals was carried out by a chemical extraction process. A quasi-in situ XRD approach was utilized to monitor the structural evolution during the Li-ion extraction process, which exhibited the progression of phases widely established for this system, but also shows evidence of inhomogeneous delithiation mechanism. Transport measurements confirm metallic behavior for delithiated Li_<i>x</i>CoO₂ crystals (0.5 < <i>x</i> < 1.0) with anomalies in the temperature of 150–180 K

Review of Study on the Coupled Dynamic Performance of Floating Offshore Wind Turbines

Floating offshore wind turbines (FOWT) have attracted more and more attention in recent years. However, environmental loads on FOWTs have higher complexity than those on the traditional onshore or fixed-bottom offshore wind turbines. In addition to aerodynamic loads on turbine blades, hydrodynamic loads also act on the support platform. A review on the aerodynamic analysis of blades, hydrodynamic simulation of the supporting platform, and coupled aero- and hydro-dynamic study on FOWTs, is presented in this paper. At present, the primary coupling method is based on the combination of BEM theory and potential flow theory, which can simulate the performance of the FOWT system under normal operating conditions but has certain limitations in solving the complex problem of coupled FOWTs. The more accurate and reliable CFD method used in the research of coupling problems is still in its infancy. In the future, multidisciplinary theories should be used sufficiently to research the coupled dynamics of hydrodynamics and aerodynamics from a global perspective, which is significant for the design and large-scale utilization of FOWT

Prediction and Experimental Evidence for Thermodynamically Stable Charged Orbital Domain Walls

On theoretical grounds, we show that orbital domain walls (ODWs), which are known to exist in the charge and orbital ordered layered manganite LaSr_{2}Mn_{2}O_{7}, should be partially charged as a result of competition between orbital-induced strain and Coulomb repulsion. This unexpected result provides the necessary condition for the known thermodynamic stability of these ODWs, which are unlike the more typical domain walls that arise only from an external field. We offer experimental data consistent with this theoretical framework through a combined transport and x-ray-diffraction study. In particular, our transport data on this charge and orbital ordered manganite exhibit abrupt transformations to higher conductance at a threshold electric field. As transport phenomena closely resemble effects found for sliding charge-density waves (SCDWs) in pseudo-one-dimensional (1D) materials, a SCDW along such pseudo-1D ODWs provides a natural explanation of our data. Importantly, x-ray-diffraction data eliminate heating and melting of charge order as tenable alternative explanations of our data