Blade Length Research Articles

Wave‐driven plant reconfiguration modifies light availability in seagrass meadows

AbstractSeagrasses are considered foundation species in marine and estuarine ecosystems by contributing biomass, providing habitat, and damping waves and currents. Globally, seagrass health and primary productivity are threatened by factors that affect light availability, such as shading by algae and epiphytes, self‐shading, and increased water column turbidity. This study focuses on how plant motion and reconfiguration lead to shading of an individual plant by itself and its neighbors, and how wave conditions, plant material properties, and shoot density affect light availability along a seagrass blade. We use a simple ray‐optics shading model with the plant motion model of Zhu et al. (2020; Journal of Geophysical Research: Oceans 125:e2019JC015517) for a flexible blade under wavy flow to understand how phase‐resolved plant behavior affects light availability as a function of vertical location in the water column. Results show that that shading of a plant by its neighbors occurs more under wave crests and troughs, and that factors that increase blade tip excursion (large wave height or wave period, or high plant flexibility) reduce light exposure. We develop a simplified theory and parameterization for average light exposure as a function of flow and plant conditions (as captured by the Cauchy number, buoyancy parameter, and ratio of stem spacing to blade length). These results help delineate optimal conditions for maximizing light exposure to seagrass' photosynthetic tissue in restoration projects, and facilitate the inclusion of flow‐vegetation interactions in biological models of seagrass production.

A Review on Performance Calculation and Design Methodologies for Horizontal-Axis Wind Turbine Blades

The efficient, low-cost, and large-scale development and utilization of offshore wind energy resources is an inevitable trend for future growth. With the continuous increase in the scale of wind turbines and their expansion into deep-sea locations, there is an urgent need to develop ultra-long, flexible blades suitable for future high-capacity turbines. Existing reviews in the field of blade design lack a simultaneous focus on the two core elements of blade performance calculation and design methods, as well as a detailed evaluation of specific methods. Therefore, this paper reviews the performance calculation and design methodologies of horizontal-axis wind turbine blades from three aspects: aerodynamic design, structural design, and coupled aero-structural design. A critical introduction to various methods is provided, along with a key viewpoint centered around design philosophy: there is no global optimal solution; instead, the most suitable solution is chosen from the Pareto set according to the design philosophy. This review not only provides a concise and clear overview for researchers new to the field of blade design to quickly acquire key background knowledge but also offers valuable insights for experienced researchers through critical evaluations of various methods and the presentation of core viewpoints. The paper also includes a refined review of extended areas such as aerodynamic add-ons and fatigue characteristics, which broadens the scope of the review to touch on multiple research areas and inspire further research. In future research, it is crucial to identify new key issues and challenges associated with increased blade length and flexibility, address the challenges faced in integrated aero-structural design, and develop platforms and tools that support multi-objective optimization design of blades, ensuring the safe, stable, and orderly development of wind turbines.

Numerical analysis of transonic flow over the FFA-W3-211 wind turbine tip airfoil

Abstract. Modern wind turbines are the largest rotating machines ever built, with blade lengths exceeding 100 m. Previous studies demonstrated how the flow around the tip airfoils of such large machines reaches local flow Mach numbers (Ma), at which the incompressibility assumption might be violated, and, even in normal operating conditions, local supersonic flow could appear. In the present study, a numerical analysis of the FFA-W3-211 wind turbine tip airfoil is performed. The results are obtained by means of the application of numerical tools: (1) XFOIL with the Prandtl–Glauert compressible correction and (2) computational fluid dynamic (CFD) simulations, where an unsteady Reynolds-averaged Navier–Stokes (URANS) model is used. A preliminary validation of the latter CFD model is performed to demonstrate that the URANS approach is a viable method for predicting the aerodynamic performances in compressible and transonic flow that provides additional and more reliable information compared to the classical compressibility corrections. From this study, three key findings can be highlighted. Primarily, the main transonic features of the FFA-W3-211 wind turbine tip airfoil have been assessed, selecting specific test cases of particular industrial interest. Then, the threshold between subsonic and supersonic flow is provided, considering also an increase of the Reynolds number (Re) from a characteristic value used in the wind tunnel experiments to the one realistic for large rotors. A strong dependence on this quantity is observed, revealing that, for the same Mach number, also the Reynolds number plays a crucial role in promoting the occurrence of transonic flow. Finally, the possible presence or absence of shock waves was investigated. The results indicate that the appearance of transonic flow is a necessary but not a sufficient condition to lead to shock formation.

Morpho-metric characterization of oat genotypes (Avena sativa L.) for agricultural sustainability under changing climatic conditions

In the present investigation, DUS (distinctness, uniformity, stability) characterization of 112 oat genotypes performed using 29 qualitative and quantitative descriptors showed a wide range of genetic diversity, with stable expression under both seasons, but main culm pithiness had no variation and all the genotypes were without pith. High variability was reported for lowest leaves, hairiness of sheaths, leaf color, flag leaf blade width and plant height. Correlation analysis revealed that 1000 seed weight was highly significant and positively associated, while plant height positively correlated with early plant growth habits, flag leaf blade length, and main culm peduncle length. The dendrogram was constructed for 112 oat genotypes and grouped these genotypes into eight clusters. The maximum genotypes were grouped into cluster 2 with 55 genotypes, and minimum numbers were found in clusters 1 and 8 with two genotypes in each cluster. The study will be helpful for breeders in deciding efficient methods and strategies for future oat improvement and selecting primary material for the hybridization program.

Morphological performance of local upland rice accessions from West Bangka for germplasm conservation

The genetic diversity of upland rice in West Bangka plays a crucial role in food security and germplasm conservation. This study aimed to identify the morphological characteristics of upland rice accessions from West Bangka. The research involved identifying seven local rice accessions from West Bangka and was conducted from March to July 2024. This study employed survey methods and field observations using Purposive Random Sampling based on type or accession, and data analysis was carried out through experimental methods. Data collection involved observing the morphology of the upland rice plants qualitatively and quantitatively. Data analyses were performed using variability tests. Local upland rice accessions in West Bangka Regency showed morphological diversity as indicated by the value of the broad variability in leaf width, leaf blade length, seed width, and seed thickness, while other traits showed narrow variability. The wide morphological diversity in certain characters showed that local accessions of upland rice in the West Bangka Regency had good genetic potential for utilization in plant breeding programs. Keywords: genetic resources; morphology; biodiversity conservation; agronomy; genetic variation

Spatiotemporal variability in the population demography of the golden kelp, Laminaria ochroleuca (Phaeophyceae), at its leading range edge

ABSTRACT Ocean warming is driving poleward range shifts for many marine species. For foundation organisms that underpin the wider ecosystem, such as canopy-forming seaweeds, shifts in distributions or population demography can have widespread ecological consequences. The warm water kelp, Laminaria ochroleuca, is found towards its leading edge in Plymouth Sound (southwest England, UK), where it has proliferated in recent years, partially replacing the cool-water congeneric species, L. hyperborea, at some wave-sheltered locations. To determine how ecosystem dynamics have changed due to this substitution and to benchmark population structure, monthly surveys were conducted of L. ochroleuca populations at three sites over 10 months. Canopy-forming L. ochroleuca sporophytes were recorded in all months at all sites, in densities of up to ~8 individuals m‒2, indicating that this species is now a conspicuous space occupier within this ecosystem. Blade length, weight and fertility followed clear seasonal patterns peaking during late spring/early summer and rapidly declining in autumn/winter. Between-site variability was also observed, with greater densities, blade lengths/widths and standing stock biomass at the most wave-sheltered but tidally influenced site. The most abundant herbivore associated with L. ochroleuca was the blue rayed limpet, Patella pellucida, which was predominantly found in summer months and in greater abundance than reported values for other kelps in the region. Our survey wide estimates of carbon standing stock ranged from 408 ± 67 to 1006 ± 181 g C m‒2 across sites, with a regional mean of 615 g C m‒2, which was in line with previous estimates for the congeneric L. hyperborea at nearby sites. Overall, the most detailed demographic assessment of L. ochroleuca to date is provided, which allows for a greater understanding of its ecological role within the wider temperate ecosystem and serves as a robust baseline against which to detect future ecological changes.

The effect of swallow guano application on the growth of mustard plants (Brassica juncea L.)

This study aims to determine the effect of giving swallow guano on the growth of mustard greens (Brassica juncea L.) using the dose that produces the best growth of mustard greens (Brassica juncea L.). This type of experimental research used a completely randomised design (CRD), X0 (control), X1 (122 grams), X2 (245 grams) and X3 (490 grams) each with 6 repetitions. The population in this study were all mustard plants with a total sample of 24 plants. Parameter measurements performed consisted of plant height, leaf length, leaf width, number of leaves and fresh weight. The data analysis technique was descriptive analysis and the BJND advanced test was carried out for analysis of variance. The results of the descriptive analysis of mustard plant growth from the 22nd HST measurement to the 40th HST experienced an increase in the graph with treatment X2 (245 grams) giving the best treatment for measuring plant height parameters, namely 40.63 cm, leaf length 25.81 cm, leaf width 16.06 cm, the number of leaves is 9.8 and the wet weight is 149.5 grams. The results of the analysis of variance from the 22nd HST to the 40th HST obtained the results of Fhit > Ftab. The results of the BJND HST test showed that treatment X2 (245 grams) gave a real treatment of measuring the parameters of plant height, length, width, and number of leaf blades and wet weight, compared to treatments X1 (122 grams) and X3 (490 grams).

Characterization of frost-tolerant plum genotypes (Prunus domestica L.) in Nishabur region, Iran: a morphological and phenological assessment following natural spring frost event

BackgroundThe Nishabur region in Iran is an ancient hub for plum production, home to numerous seedling orchards and indigenous plum varieties. In 2020, an evaluation was conducted in the primary plum-growing zones of Nishabur following a harsh spring frost. Forty-one plum genotypes and local varieties capable of bearing fruit after frost incidents were selected for further examination. These plum selections were evaluated based on 60 morphological, pomological, and phenological traits related to flowers, fruits, and trees, in accordance with the UPOV (2020) plum descriptor.ResultsAmong the 41 genotypes evaluated, 35 exhibited high yields, demonstrating their potential as viable options for cultivation in frost-prone areas. The highest coefficient of variation (39.45%) was observed in the fruit color. Several genotypes demonstrated acceptable pomological traits. The genotype ‘Kh.Da.cv.04‘ has the highest values in terms of fruit weight (56.2 g), fruit width (46 mm), and fruit length (61 mm). Significant positive correlations were found between fruit length and leaf length and fruit weight and leaf blade length. Factor analysis revealed that fruit weight, size, and leaf length are the most influential factors, accounting for 52% of the total variance. In the principal component analysis (PCA), genotypes were clustered into four main groups, with ‘Kh.Da.s.02’ and ‘Kh.Da.cv.04’ positioned at the positive end of the second axis, separate from the other genotypes. Cluster analysis indicated that these genotypes, along with ‘Ha.Bokh.cv.30’, formed distinct clusters, considerably distant from the other genotypes, which were grouped into four main clusters.ConclusionsThis research highlights the presence of frost-tolerant genotypes and varieties with suitable environmental adaptability in the Nishabur region, demonstrating relatively acceptable diversity. These genotypes hold potential for breeding and germplasm conservation purposes.

An efficient automated measurement method for aero-engine fan blade geometric parameters

The length of aero-engine fan blades usually exceeds 1 m, making contact-based coordinate measuring machines (CMM) costly and time-consuming. To enhance measurement efficiency and accuracy, we developed a large-field flexible measurement system. We propose the system calibration method using a standard sphere as the reference and taking the turntable axis into account. A model-driven path planning and multi-view data fusion (MVDF) strategy was introduced to enhance efficiency and reduce misalignment due to the robotic arm’s lower positioning accuracy. To improve cross-sectional data sorting and thinning, we proposed an adaptive threshold synchronous sorting and noise suppression method. Additionally, we developed algorithms for chord length and maximum thickness extraction to streamline the process. Experiments show improved accuracy for blade thickness (0.092 mm) and chord length (0.096 mm).

Energy-resolved neutron imaging study of a Japanese sword signed by Bishu Osafune Norimitsu

Our research focuses on elucidating the crystallographic structure of Japanese swords in a nondestructive manner using the neutron imaging instrument RADEN at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC). We developed an analysis method combining wavelength-resolved Bragg-edge imaging and wavelength-selective neutron tomography with a new strategy and applied it to an approximately 45-cm blade length Japanese sword signed by Bishu Osafune Norimitsu. Computed tomography was performed, and the three-dimensional analysis captured the characteristic internal structure of Kobuse. Kobuse is the most famous steel-combining structure of Japanese swords, where an outer steel with high-carbon content (Kawagane) covers a core steel with low-carbon content (Shingane). The crystallite size distribution obtained through Bragg-edge analysis could consistently explain the internal structure of two steels observed in neutron tomograms. Our nondestructive imaging revealed deep hardening, forming a wavy pattern more than 5 mm from the cutting edge.

Wave exposure influences kelp morphological and biomechanical phenotypic plasticity

Despite global and local declines in kelp ecosystems, luxuriant kelp beds persist at the Eastern Shore Islands (ESI) in Nova Scotia, Canada. Kelp beds in other regions of Nova Scotia were defoliated as the invasive bryozoan Membranipora membranacea and warming temperatures weakened kelp tissues and enhanced erosion and dislodgment. We propose that the high wave exposure at the ESI causes morphological and biomechanical phenotypic plasticity of kelp tissues. We compared differences in morphology and mechanical properties of the kelps Laminaria digitata and Saccharina latissima across 3 sites with different wave exposures, and differences in mechanical properties across blade lengths. Both species showed morphological plasticity; higher wave exposure resulted in longer and thicker stipes and thicker blades with increased branching. The mechanical properties of L. digitata showed increased breaking stress (strength) and strain (extensibility) with higher wave exposure, whereas S. latissima did not show mechanical plasticity with increasing exposure. For both species, blades were weaker but more extensible at the meristem and stronger but less extensible near the distal end of the blade. Larger and stronger kelp from high-exposure areas may promote the persistence of kelp beds in the ESI despite local stressors.

Numerical investigation on boiling crisis characteristic of a 7-rod HCF assembly in hexagonal lattice

Helical cruciform fuel (HCF) has the advantages of larger heat transfer area, enhanced coolant mixing and self-supporting, which contribute to increasing power density and safety margins. Compared with the square lattice configuration, the hexagonal arrangement of HCF assembly is more compact, which can help achieve a higher power density. In this paper, the flow characteristics and heat transfer behaviors of HCF in hexagonal lattice were predicted at high and low vapor quality during boiling crisis based on Eulerian two-fluid model. The influence of twist pitches and cross-sections of the fuel rod on heat transfer efficiency and fuel temperature was also studied. The cross-flow intensity changed periodically with a 30° cycle at low vapor quality, and did not fluctuate periodically at high vapor quality, which decreased with the increase of flow resistance. The highest heat flux of HCF rod was the at the blade root and the lowest was at the blade tip, and the maximum to average heat flux ratio was about 1.8. The peak vapor fraction and temperature occurred at leeside side of the fuel rods. The increase of the twist pitch reduced the critical heat flux (CHF), and the increase of blade length enhanced the non-uniformity of heat flux distribution. During boiling crisis, the maximum temperature of the fuel was lower than the phase transition temperature of U-50 wt%Zr alloy, which means the cladding meltdown caused by boiling crisis will occur before phase transition of the fuel.

Structural dynamic characteristics of vertical axis wind and tidal current turbines

Vertical axis turbines have received great attention in both offshore wind and tidal current energy communities considering their advantages of economic design and unidirectional operation. However, their commercialization process is rather slow compared with the development of horizontal axis turbines due to technical challenges resulting from higher loads from unsteady aero/hydrodynamic forces, centrifugal forces and gravity of the structures. These are mainly because, while the inherent unsteady tangential pulls and fatigue loads intensify the structural vibration, aggravating structural safety and fatigue life, the relationship between the geometric parameters and the structural responses of blades remains unclear. Therefore, in order to clarify this issue, in this study, we focus on the modal and transient analysis of vertical axis turbines using multi-body dynamics, geometrically exact beam theory and detached eddy simulation. We find that the natural frequency of the rotor is directly related to the ratio of blade length and arm length. The effect of arms cannot be ignored in the structural analysis of the turbine. Moreover, an increase of blade length intensifies the deformation and vibration of the turbine’s structure, making the turbine more prone to fatigue failure. This article is expected to extend the existing knowledge of wind and tidal current turbines and provide a reference for choosing proper design parameters and developing suitable-capacity vertical axis turbines.

Twist and chord optimization using the linearization method on the taper blade of a micro-horizontal axis wind turbineTwist and chord optimization using the linearization method on the taper blade of a micro-horizontal axis wind turbine

The research aims to optimize the geometry of taper blade profiles for the Horizontal Axis Wind Turbine (HAWT) to improve aerodynamic performance and minimize fabrication complexity. The study used blade linearization as an optimization method for identifying a desirable twist (β) and chord (Cr). This approach enhances accuracy and boosts computational efficiency. It simplifies the optimization process by reducing complexity. In contrast, traditional nonlinear methods are slower and more resource-intensive due to complex aerodynamic interactions. The best β and Cr distributions were found by linearization with elements 1 and 10 of the blade length and positions 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85, and 95% of the blade elements. The linearization results were used to determine the optimum performance of the HAWT design using simulation. The optimal blades for HAWT were fabricated and their performance evaluated under real wind conditions. The linearization of the 45% twist and chord of elements 1 and 10 provided the best blade shape. Optimized twist and chord yielded HAWT performance with the Cp of 45% to 47% at rotational speeds of 200–900 rpm and wind speeds of 2–10 m/s. Twist and chord optimization increased the Cp from 39.71% to 46.43% with a rotational speed of 550 rpm at a wind speed of 6 m/s, as well as the maximum mechanical power from 424.28 watts to 500.35 watts at a wind speed of 10 m/s. The result from real wind conditions showed that manufactured HWAT produced an average electrical power of 294.19 watts at a rotational speed of 590.66 rpm. These results demonstrate that the optimized design approach presents a close match and is still reasonable in comparison to practical conditions.

Numerical Simulation and Model Test on Pressure Fluctuation and Structural Characteristics of Lightweight Axial Flow Pump

In order to explore the relationship between the hydraulic performance, pressure pulsation, and structural characteristics of lightweight axial flow pumps, this paper takes the axial flow pump as the research object and analyzes pressure pulsation and structural characteristics by changing the blade length and thickness to realize the lightweight design of the axial flow pump impeller. Compared with the initial scheme (Scheme 1), the mass of the impeller is reduced by 17.2% (Scheme 2) and 29.9% (Scheme 3), respectively. The lightweight axial flow pump (Scheme 2 and Scheme 3) has a lower pressure pulsation amplitude at the impeller outlet monitoring point under large flow conditions. After the lightweight design of the axial flow pump impeller, the blade becomes shorter, the mass becomes lighter, and the cavitation performance will become worse. The maximum equivalent stress of Scheme 2 and Scheme 3 is increased by 2.8% and 31.9%, respectively, compared to Scheme 1. The maximum deformation of Scheme 3 increased by 27% compared to Scheme 1. This research can provide guidance for the lightweight optimization design of the axial flow pump.

An integrative taxonomic revision of the Chaerophyllum hirsutum complex (Apiaceae) using morphological and molecular markers

Background and aims – Chaerophyllum hirsutum represents a complex of taxa with varying treatments and ranks across floras. Using both morphometric and molecular markers, we assessed the robustness of C. hirsutum, C. elegans, C. villarsii, and C. villarsii var. cicutariiforme. Material and methods – Ten morphometric variables and two ratios were calculated. Based on the sequencing of six plastomes, the rps16 intron was selected as the more variable region and sequenced on a broader sampling. Additionally, we also sequenced the nrDNA internal transcribed spacer 2 (ITS2) using Illumina technology to obtain intra-individual allelic diversity. Key results – Morphologically, the most easily differentiated taxon was C. elegans, especially using the number of subterminal umbels. The distinction between C. hirsutum and C. villarsii was rather clinal, but is mainly based on the degree of carpophore division. Finally, C. villarsii var. cicutariiforme was less easily distinguishable from the three others, but partly using the carpophore length and the total length of basal leaf blade. The cpDNArps16 clearly distinguished C. elegans from the three other taxa of the complex, which rather showed a geographical pattern of cpDNA diversity. The nrDNA ITS2 partially distinguished C. villarsii from the other taxa, without distinction of C. elegans. Conclusions – The present study supports the species differentiation of C. elegans based on both morphology and chloroplast genome. Furthermore, C. villarsii var. villarsii and C. villarsii var. cicutariiforme could potentially be recognized as distinct varieties within C. hirsutum. This will need to be confirmed by future studies using a larger sampling size and more comprehensive markers, covering a broader portion of the nuclear genome.

A Physiological Analysis of Desiccation Stress in the Green Tide Species Ulva stenophylloides and Ulva uncialis in the South Pacific

Global green tide blooms of the Ulva genus have been increasing due to human activities, with mass accumulation in Algarrobo Bay, Chile, causing ecological and social issues. In this area, five Ulva species were previously identified, with Ulva stenophylloides dominating across seasons and intertidal zones; Ulva uncialis was the second most abundant, mainly in winter. In this study, we tested the hypothesis that U. stenophylloides is more tolerant to desiccation than U. uncialis, explaining its dominance in the upper intertidal zone. Based on in vitro cultures, we assessed the impact of desiccation stress on weight, blade length, cellular activity, and lipoperoxide levels. In U. uncialis, desiccation treatment caused a decrease in weight; conversely, in U. stenophylloides, both control and desiccation treatments caused a slight decrease in weight. No significant differences (p > 0.05) in blade length or lipoperoxide levels as a function of culture time were detected in the control and desiccation treatment groups for both species. Furthermore, desiccation had no negative effects on the cellular activity of either species. Although the observed weight changes suggest that U. uncialis is more desiccation-tolerant than U. stenophylloides under the experimental conditions, the cellular activity and lipoperoxidation indicate high desiccation tolerance in both species, which partly explains their intertidal dominance.

Evaluation of the diversity of the morpho-agronomic characteristics of Corchorus olitorius L. cultivars developed in Saudi Arabia

Corchorus olitorius is considered a crop with high nutritional value. The C. olitorius crop is cultivated in many regions of Saudi Arabia. There is a lack of research on genetic diversity among these varieties. This work aimed to evaluate the diversity in the morphological characteristics of KSA jute germplasms and compare them to international germplasms. This study included 8 local jute germplasm seeds collected in Saudi Arabia and 16 international jute germplasm seeds from Asia, Africa and the USA. Twenty-one quantitative and qualitative characteristics of the jute samples from the stem, leaves, and fruits were evaluated. These characteristics were evaluated using many reliable statistical methods, such as multivariate analysis and one-way analysis of variance (ANOVA). Morphological traits, especially plant height, days to 50% flowering, leaf blade length, leaf blade width, leaf petiole length, pod pedicel length, pod length, pod width, number of pods per plant and leaf area, significantly differed among the jute samples. This is the first study to compare local jute germplasms in the KSA to international, to provide important information on their morphological diversity. This information can be used in crop improvement and conservation programs.

The impact of extreme wind conditions and yaw misalignment on the aeroelastic responses of a parked offshore wind turbine

As global energy demands rise and the urgent need to reduce carbon emissions, offshore wind energy technology has evolved rapidly, becoming a vital component of the world’s energy portfolio. However, offshore wind turbines face new challenges due to complex marine environments. Under extreme conditions such as strong winds and yaw misalignment, parked wind turbines exhibit complex aerodynamic and structural responses that significantly differ from those in normal operating conditions. These responses, crucial to the integrity and safety of wind turbines, demand thorough analysis. This article presents an in-depth aeroelastic analysis of a parked 5 MW offshore wind turbine using a sophisticated and precise numerical model. It explores the impacts of incoming wind speed and yaw misalignment on the aerodynamic loads and structural behaviors of the wind turbine. The findings indicate that gravity plays a significant role in blade structural responses for a parked wind turbine. Additionally, higher wind speeds elevate aerodynamic forces, leading to more pronounced fluctuations in root forces and tip deflections. The increase in wind speed triggers and exacerbates high-frequency edgewise vibrations of the blade, further leading to fluctuations and instability in the loads. The study also reveals that yaw misalignment causes the AOA changes significantly over time, and generates intermittent fluctuations in lift and drag, leading to extra blade vibrations with the maximum amplitude exceeding 10% of the blade length. This research enhances the current understanding of the operational safety of offshore wind turbines, particularly under extreme conditions. It aims to provide valuable insights and guidance for researchers and developers in designing and monitoring the performance of offshore wind turbines, ensuring their resilience and efficiency in challenging environments.

Damage evolution simulation and lifetime prediction for composite blades under continuous droplet impacts

Offshore wind power generation is a promising technology in renewable energy applications due to its high reserves of wind energy in sea areas. To improve the energy transformation efficiency, the blade length of the offshore wind turbines has become larger and larger, and it has made rain erosion be one of the most frequent failures during the turbine operation. As the natural rainfall is stochastic in spatial and time domains, it is difficult to depict the damage evolution process caused by rain impact exactly. Therefore, regular and continuous droplet impact simulation and experiments present an alternative methodology for this issue. With the composite structure of the blade and deformability of the liquid droplet in consideration, a fluid solid interaction model will be established to investigate the impact response and subsequent damage evolution. In which, the Smooth Particle Hydrodynamics (SPH) model is utilized to depict the constitutive relationship within the droplet, and Finite Element Method (FEM) is used to construct the Representative Volume Element (RVE) model of the blade leading edge. The impact process is simulated first to obtain the impact pressure distribution at the contact center and velocity field in the droplet. Furthermore, the stress wave propagation in the blade multilayer structure can be analyzed. Owing to the multiaxial fatigue feature of the continuous droplet impact, the continuum damage mechanics is integrated with the fatigue criterion and the Jump-in-Cycle procedure is used to simulate the high-cycle fatigue process. The damage factor distribution on the blade coating surface and its influence on mechanical properties are analyzed. Thereafter, the droplet impact fatigue life can be accumulated based on Miner’s linear rules. The theoretical achievements are validated by experimental data provided by Rain Erosion Testing (RET), which shows a good agreement between each other. As a result, V-N curves and D-N curves, i.e. quantitative relationship between droplet falling conditions and impact fatigue life, are established. The achievements in this study can provide an effective tool for rain erosion mechanism analysis and life prediction in industrial applications.