Investigating structural behavior of wind turbine composite blade using FSI method

The wind turbine blades are exposed under complex time-variant aero-dynamic loads, besides, due to the complexity of its aero-dynamic shape, the study on blade dynamic responses can be sophisticated. To achieve a more realistic simulation and with credible results, a FSI analysis is necessary for resolving the coupling effects between the blade structure and the surrounding flow, and thus examine the load impacts to the blade structure itself by having e.g. stress distribution and strain. A typical structural layout of a composite blade is shown in Fig 4(a). From the cut-plane view, the blade is composed by 6 sections on the chord-line direction, supported by 2 bearing structures between the up and down blade surfaces. For each section, materials with different mechanical properties and stacking orders are applied. This will lead to a sophisticated modeling process

OC6 project phase III : validation of the aerodynamic loading on a wind turbine rotor undergoing large motion caused by a floating support structure

This paper provides a summary of the work done within Phase III of the Offshore Code Comparison, Collaboration, Continued, with Correlation and unCertainty project (OC6), under International Energy Agency Wind Task 30. This phase focused on validating the aerodynamic loading on a wind turbine rotor undergoing large motion caused by a floating support structure. Numerical models of the Danish Technical University 10-MW reference wind turbine were validated using measurement data from a 1:75 scale test performed during the UNsteady Aerodynamics for FLOating Wind (UNAFLOW) project and a follow-on experimental campaign, both performed at the Politecnico di Milano wind tunnel. Validation of the models was performed by comparing the loads for steady (fixed platform) and unsteady wind conditions (harmonic motion of the platform). For the unsteady wind conditions, the platform was forced to oscillate in the surge and pitch directions under several frequencies and amplitudes. These oscillations result in a wind variation that impacts the rotor loads (e.g., thrust and torque). For the conditions studied in these tests, the system mainly described a quasi-steady aerodynamic behavior. Only a small hysteresis in airfoil performance undergoing angle of attack variations in attached flow was observed. During the experiments, the rotor speed and blade pitch angle were held constant. However, in real wind turbine operating conditions, the surge and pitch variations would result in rotor speed variations and/or blade pitch actuations depending on the wind turbine controller region that the system is operating. Additional simulations with these control parameters were conducted to verify the fidelity between different models. Participant results showed in general a good agreement with the experimental measurements and the need to account for dynamic inflow when there are changes in the flow conditions due to the rotor speed variations or blade pitch actuations in response to surge and pitch motion. Numerical models not accounting for dynamic inflow effects predicted rotor loads that were 9 % lower in amplitude during rotor speed variations and 18 % higher in amplitude during blade pitch actuations

A general FSI framework for an effective stress analysis on composite wind turbine blades

The fluid-structure interaction (FSI) technique has been extensively used and developed in the past decades. Commonly, the reduced-order models are used in FSI analyses to assure the numerical robustness and efficiency. However, due to the increasing demand for higher numerical resolutions in modern wind turbine composite blade applications, intrinsic limitations of reduced-order models, such as their inability to account for complex aerodynamic flow interactions, multi-motion couplings, and sophisticated composite properties, have become the weaknesses in existing reduced-order FSI approaches. In this study, we propose a general FSI framework, which combines the advantages of high-fidelity Computational Fluid Dynamics (CFD) and robust Multi-Body Dynamics (MBD) methods, and detailed Finite Element Analysis (FEA) for analysing the detailed stress distributions on the composite structures. The results of predicted dynamics and the Von Mises stress on the composite blade structures under given operation condition are compared and reasonably agreed with the literature results, with a significant computational cost reduction by nearly 25% is achieved. The proposed FSI framework can be a general approach to investigate the multi-physical interactions where the composite structure specifications are involved, coupling with complex dynamic motions in three-dimensional space

Influence of Afterburner Coated with Absorbing Material on Radar Scattering Characteristics of Engine Exhaust System

In order to improve the backward-facing radar stealth capability of the engine exhaust system, five coating schemes for afterburner, which is radar wave strong scattering source, are formulated. The influence of afterburner coating absorbing materials on the horizontal polarization and vertical polarization RCS distribution pattern of the exhaust system in the range of -30°~+30° azimuth of the typical frequency point in the S-band and X-band is analyzed by using the shooting and bouncing rays, also SAR imaging of typical frequency points in the X-band at an azimuth angle of 0° is simulated.The results show that the distribution of strong scattering sources in S-band and X-band is basically the same, and the influence of different coating schemes of absorbing materials on the RCS reduction effect of two bands is similar. The flame stabilizer is the strongest scattering source of radar characteristic signal, and coating it with radar absorbing materials has the greatest benefit on reducing the radar characteristic signal of the exhaust system. Coating absorbing materials in the four parts of afterburner inner cone, flame stabilizer, lobe mixer and afterburner cylinder is the best absorbing material coating scheme for the reduction effect of RCS in the two wave bands. The average RCS reduction effect of horizontal polarization and vertical polarization in S band is 92.3% and 92.0%, and the average RCS reduction effect of horizontal polarization and vertical polarization in X-band is 90.2% and 88.4%

The Application of Pediatric Ureteroscope for Seminal Vesiculoscopy

To describe a novel technique of transurethral seminal vesiculoscopy using a pediatric ureteroscope in the diagnosis and management of persistent hematospermia, a retrospective study was carried out for 20 patients with recurrent hematospermia whom we evaluated and treated using a 6–7.5F (6F front end and 7.5F rear end) pediatric ureteroscope from August 2009 to September 2013. For the 20 patients, the age ranges from 25 to 48 years with a mean age of 36 years. The duration of the hematospermia ranges from 6 to 48 months with a mean duration of 18 months. Transurethral seminal vesiculoscopy was successfully performed in the 20 cases and the mean operative time was 35 min (ranges from 25 to 90 min). Among the 20 patients, 11 patients were found to have seminal vesiculitis, five were with seminal vesicle stone, one was with prostatic utricle stone, one was with prostate cyst, and one was with ejaculatory duct obstruction. The mean follow-up period was 7 months (ranged from 6 to 12 months). Hematospermia in 19 cases disappeared after the surgery and only in one patient the hematospermia recurred 6 months after the surgery. The cure rate was 95%. This study indicated that transurethral seminal vesiculoscopy could be performed easily using a semirigid pediatric ureteroscope with few complications and is an effective therapeutic approach for persistent hematospermia

The multi-consecutive optical bottles generated from the chirped elliptical Pearcey Gaussian vortex beams

The evolution of the chirped elliptical Pearcey Gaussian vortex (CEPGV) beams in free space is numerically investigated. The optical bottle and multi-consecutive optical bottles can be directly generated from an elliptical Pearcey Gaussian beam with central vortices and the second-order chirp. In particular, the focusing intensity of CEPGV beams will increase when the elliptical structure deflects larger or the ratio of the long axis to the short axis of the ellipse is larger. Furthermore, we can obtain multi-consecutive optical bottles by manipulating elliptical structure parameters and second-order chirp factors. In the meantime, the transverse intensity distributions at foci of CEPGV beams appear like a slit in a fixed direction. Our results show that the focusing intensity, the focal length and the transverse intensity distribution of CEPGV beams during the propagation can be controlled

New insights into the transfer and accumulation of dioxins and dioxin-like PCBs in the food web of farmed Chinese mitten crabs : A typical case from the Yangtze River area

Dioxins and dioxin-like polychlorinated biphenyls (DL-PCBs) transfer and accumulation behavior remains poorly understood in the farmed Chinese mitten crab (Eriocheir sinensis). In this study, dioxins and DL-PCBs concentration in 48 farming crabs in lower reaches of the Yangtze River was monitored and controlled field design was conducted in a typical farm to dissect the dioxins and DL-PCBs contamination in crab food web (crab, feeds, and environment). Results showed that dioxins and DL-PCBs were ubiquitous in farmed crabs with concentrations ranging from 0.390 to 37.2 pg toxic equivalents (TEQ) g−1 ww and do not present a health risk to general consumers. Of the total dioxins TEQ found in crab in treated farms, 45.6% was attributed to direct transfer from the aquaculture environment and 46.5% to the consumption of snails. Consumption of feed material accounted for nearly all of the total DL-PCBs TEQ, divided as 58.2% from feed and 41.8% from snails. These results demonstrated that dominant routes of dioxins accumulation in crabs were transferred for the sediment-snail-crab and sediment-crab chains, whereas DL-PCBs is mainly transferred through consumption of feeds and snails. To our knowledge, this work is the first report of snails serving as a biomagnification medium that promotes accumulation of dioxins in mitten crabs. This observation provided crucial insight to prevent and reduce contamination of crab by dioxins and DL-PCBs

Various applications of TALEN- and CRISPR/Cas9-mediated homologous recombination to modify the Drosophila genome

Modifying the genomes of many organisms is becoming as easy as manipulating DNA in test tubes, which is made possible by two recently developed techniques based on either the customizable DNA binding protein, TALEN, or the CRISPR/Cas9 system. Here, we describe a series of efficient applications derived from these two technologies, in combination with various homologous donor DNA plasmids, to manipulate the Drosophila genome: (1) to precisely generate genomic deletions; (2) to make genomic replacement of a DNA fragment at single nucleotide resolution; and (3) to generate precise insertions to tag target proteins for tracing their endogenous expressions. For more convenient genomic manipulations, we established an easy-to-screen platform by knocking in a white marker through homologous recombination. Further, we provided a strategy to remove the unwanted duplications generated during the “ends-in” recombination process. Our results also indicate that TALEN and CRISPR/Cas9 had comparable efficiency in mediating genomic modifications through HDR (homology-directed repair); either TALEN or the CRISPR/Cas9 system could efficiently mediate in vivo replacement of DNA fragments of up to 5 kb in Drosophila, providing an ideal genetic tool for functional annotations of the Drosophila genome