Aspergillus carbonarius is a major producer of ochratoxin A in grapes, causing fungal decay and posing a significant threat to human health. Bacillus subtilis CCTCC M 207209 was used to inhibit the ...growth of A. carbonarius CCTCC AF 2011004, an ochratoxin A-producing strain previously isolated from grapes. The inhibition effect in vitro was tested in potato dextrose agar medium (PDA), while in vivo effects were examined in grape berries of three different grape cultivars: Thompson Seedless, Kyoho, and Red Earth. Inhibitory effects were evaluated according to colony size in PDA and rotten spots in grape berries when A. carbonarius and B. subtilis were inoculated simultaneously and cultivated at 0 °C, 25 °C, or 30 °C. B. subtilis liquid cultures with and without cells and volatile products were used in the analyses. Significant inhibition of A. carbonarius was observed in all samples treated with B. subtilis liquid cultures, especially those subjected to cell-free culture treatment. No inhibition was observed for A. carbonarius treated with the volatile products of B. subtilis. The inhibition was the most significant in Red Earth grapes, followed by the Kyoho then Thompson Seedless varieties, when the same fraction of B. subtilis culture was used. Significant inhibition was also observed for other fungal contaminants in grapes when B. subtilis liquid culture supernatant was used. This study reveals the potential of B. subtilis for inhibiting contamination of OTA-producing A. carbonarius and other fungi in table grapes.
•Bacillus subtilis had significant growth inhibition of Aspergillus carbonarius in vitro and in vivo.•B. subtilis had significant growth inhibition of fungal contamination in table grape.•Both B. subtilis liquid and cell-free culture supernatant have inhibitory effect.•The inhibition effect of B. subtilis was diversity among different grape cultivars.
Passive vortex generators (VGs) have been widely applied on wind turbines to boost the aerodynamic performance. Although VGs can delay the onset of static stall, the effect of VGs on dynamic stall is ...still incompletely understood. Therefore, this paper aims at investigating the deep dynamic stall of NREL S809 airfoil controlled by single-row and double-row VGs. The URANS method with VGs fully resolved is used to simulate the unsteady airfoil flow. Firstly, both single-row and double-row VGs effectively suppress the flow separation and reduce the fluctuations in aerodynamic forces when the airfoil pitches up. The maximum lift coefficient is therefore increased beyond 40%, and the onset of deep dynamic stall is also delayed. This suggests that deep dynamic-stall behaviors can be properly controlled by VGs. Secondly, there is a great difference in aerodynamic performance between single-row and double-row VGs when the airfoil pitches down. Single-row VGs severely reduce the aerodynamic pitch damping by 64%, thereby undermining the torsional aeroelastic stability of airfoil. Double-row VGs quickly restore the decreased aerodynamic efficiency near the maximum angle of attack, and also significantly accelerate the flow reattachment. The second-row VGs can help the near-wall flow to withstand the adverse pressure gradient and then suppress the trailing-edge flow separation, particularly during the downstroke process. Generally, double-row VGs are better than single-row VGs concerning controlling deep dynamic stall. This work also gives a performance assessment of VGs in controlling the highly unsteady aerodynamic forces of a wind turbine airfoil.
Passive vortex generators (VGs) are widely used to suppress the flow separation of wind turbine blades, and hence, to improve rotor performance. VGs have been extensively investigated on stationary ...airfoils; however, their influence on unsteady airfoil flow remains unclear. Thus, we evaluated the unsteady aerodynamic responses of the DU-97-W300 airfoil with and without VGs undergoing pitch oscillations, which is a typical motion of the turbine unsteady operating conditions. The airfoil flow is simulated by numerically solving the unsteady Reynolds-averaged Navier-Stokes equations with fully resolved VGs. Numerical modelling is validated by good agreement between the calculated and experimental data with respect to the unsteady-uncontrolled flow under pitch oscillations, and the steady-controlled flow with VGs. The dynamic stall of the airfoil was found to be effectively suppressed by VGs. The lift hysteresis intensity is greatly decreased, i.e., by 72.7%, at moderate unsteadiness, and its sensitivity to the reduced frequency is favorably reduced. The influences of vane height and chordwise installation are investigated on the unsteady aerodynamic responses as well. In a no-stall flow regime, decreasing vane height and positioning VGs further downstream can lead to relatively high effectiveness. Compared with the baseline VG geometry, the smaller VGs can decrease the decay exponent of nondimensionalized peak vorticity by almost 0.02, and installation further downstream can increase the aerodynamic pitch damping by 0.0278. The obtained results are helpful to understand the dynamic stall control by means of conventional VGs and to develop more effective VG designs for both steady and unsteady wind turbine airfoil flow.
This study aims to assess the dynamic stall of the wind turbine blade undergoing pitch oscillation (PO) and oscillating freestream (OF), respectively. Firstly, a thin-airfoil theoretical analysis was ...performed to differentiate between these two dynamic effects. During upstroke, PO results in a positive effective airfoil camber, while OF has an additional negative effective airfoil camber, and yet in contrast during downstroke, PO decreases the effective camber, while OF increases the effective camber. Secondly, the equivalence relation between PO and OF is investigated by numerically solving the unsteady Reynolds-averaged Navier-Stokes equations. The difference between PO and OF mainly exists in the linear part of the aerodynamic loads. Because the difference is great at high reduced frequencies or angle of attack (AOA) amplitudes, PO and OF should be treated separately for dynamic stall from different aerodynamic sources. Thirdly, the Beddoes-Leishman dynamic model coupled with Bak’s rotational stall delay model was used to predict the yawed responses of the blade section. The obtained results show different aerodynamic responses between PO and OF, although consideration of rotational augmentation can greatly improve the accuracy of the lift and drag coefficients. To improve the understanding and coupling modeling of rotational augmentation and dynamic stall, an extended analysis of the coupled effect was performed as well.
Rotational augmentation and dynamic stall have been extensively investigated on horizontal axis wind turbines (HAWTs), but usually as separate topics. Although these two aerodynamic phenomena mainly ...determine the unsteady loads and rotor performance, the combined effect of rotational augmentation and dynamic stall is still poorly understood and is challenging to model. We perform a comprehensive comparative analysis between the two-dimensional (2D) airfoil flow and three-dimensional (3D) blade flow to provide a deep understanding of the combined effect under yawed inflow conditions. The associated 2D aerodynamic characteristics are examined by the unsteady Reynolds-averaged Navier-Stokes Simulations, and are compared with the experimental data of NREL Phase VI rotor in three aspects: aerodynamic hysteresis, flow field development, and dynamic stall regimes. We find that the combined effect can dramatically reduce the sectional lift and drag hysteresis by almost 60% and 80% from the supposed definitions of hysteresis intensity, and further delay the onset of stall compared with either of rotational augmentation and dynamic stall. The flow field development analysis indicates that the 3D separated flow is greatly suppressed in the manner of changing the massive trailing-edge separation into the moderate leading-edge separation. Furthermore, the 3D dynamic stall regime indicates a different stall type and an opposite trend of the separated zone development, compared with the 2D dynamic stall regime. These findings suggest that the modelling of 3D unsteady aerodynamics should be based on the deep understanding of 3D unsteady blade flow rather than correcting the existing 2D dynamic stall models. This work is helpful to develop analytical models for unsteady load predictions of HAWTs.
Stall, a complex phenomenon related to flow separation, is difficult to be predicted accurately. The motivation of the present study is to propose an approach to improve the simulation accuracy of ...Reynolds Averaged Navier–Stokes equations (RANS) for wind turbines in stall. The approach is implemented in three steps in simulations of the S809 airfoil and the NREL (National Renewable Energy Laboratory) Phase VI rotor. The similarity between airfoil and rotor simulations is firstly investigated. It is found that the primary reason for the inaccuracy of rotor simulation is not the rotational effect or the 3-D effect, but the turbulence-related problem that already exists in airfoil simulation. Secondly, a coefficient of the SST turbulence model is calibrated in airfoil simulation, ensuring the onset and development of the light stall are predicted accurately. The lift of the airfoil in the light stall, which was overestimated about 30%, is reduced to a level consistent with experimental data. Thirdly, the calibrated coefficient is applied to rotor simulation. That makes the flow patterns on the blade properly simulated and the pressure distribution of the blade, as well as the torque of the rotor, are predicted more accurately. The relative error of the predicted maximum torque is reduced from 34.4% to 3.2%. Furthermore, the procedure of calibration is applied to the MEXICO (Model Experiments in Controlled Conditions) rotor, and the predicted pressure distributions over blade sections are better than the CFD (Computational Fluid Dynamics) results from the Mexnext project. In essence, the present study provides an approach for calibrating rotor simulation using airfoil experimental data, which enhances the potential of RANS in accurate simulation of the wind turbine aerodynamic performance.
A numerical analysis method of trailing edge deboning is proposed in this paper. Using this method, multiple repair parameters can be quantified by analyzing aerodynamic responses and structural ...characteristics of the trailing edge. This method can be applied to three types of trailing edge, including blunt trailing edge, transitional trailing edge, and pointed trailing edge. In this study, the repair parameters are divided into two types, including the internal parameters that can affect the bonding strength and the external parameters that can affect the stiffness and aerodynamic shape. The main research steps are as follows: First, a repair structure shell‐body model was developed. Second, static tensile tests were carried out using 49 specimens, covering two lap joint types and seven bonding thicknesses. Finally, nine different repaired trailing edge models were developed using Ansys/Fluent for each two two‐dimensional airfoil. A 30–40 m section of a 71 m blade was used to develop a three‐dimensional (3D) rotating model with the repaired trailing edge. The simulation results show that the two internal parameters, overlap length and the slope of adhesive joints, are the key to improving the bonding performance of the pointed trailing edge. In addition, the bonding thickness range of 1–10 mm is proved by the experiment results and numerical analysis to be sufficient for good bonding performance. Besides this, the influence of the repair height on the aerodynamic pressure distribution and lift coefficient is much greater than the repair width, and the torque and power of the repaired 3D blade model are 1.91% higher than that of the original blade. This should further help provide an effective theoretical basis for determining the repair plan for a wind turbine blade.
Effect of repair parameters on bonding strength and the aerodynamic response of trailing edge bonding failure.
An automatic modeling method suitable for three trailing edge types is introduced to analyze the influence of repair parameters on bonding strength.
The influence of bonding strength is verified by the test of different bonding thicknesses of single lap and double lap.
The aerodynamic response changes due to slight shape deviation under two‐dimensional airfoil and three‐dimensional rotating blades are extensively analyzed.
Background
Autism spectrum disorder (ASD) is a highly disabling neurodevelopmental disorder, and the burden is high. Data on the burden of ASD are limited in China, especially in the southwest. ...Therefore, the aims of this study were to investigate the intervention status and burden of children with ASD in Southwest China.
Materials and methods
Families of children with ASD were recruited from hospitals, special education schools, and private rehabilitation centers; they participated in the survey and completed the questionnaire. Descriptive analysis was conducted on the questionnaire results, which included basic demographic characteristics, rehabilitation status, and burden. Multivariate analysis was used to analyze the association of basic family demographic characteristics, rehabilitation status, and costs of ASD.
Results
A total of 231 families of children with ASD participated in this survey, and 78.35% (181/231) of the children with ASD were male. The mean age was 4.34 ± 2.09 years. A total of 55.84% (129/231) of the children with ASD had an intellectual disability. Only 46.32% (107/231) started receiving intervention within 1 month after diagnosis. The institutions for rehabilitation interventions for children with ASD were mainly tertiary hospitals (39.39%), special education schools (29.87%) and private rehabilitation institutions (21.64%). For a total of 42.86% (99/231) of the children with ASD, the duration of the intervention was less than 10 h per week. A total of 74.89% (173/231) of the children with ASD received a rehabilitation intervention at home. A total of 66.67% of the parents were satisfied with the treatment. The monthly cost of medical intervention for the patients of children with autism was 7,225 ± 474 RMB ($1,134 ± 74), and the non-medical intervention cost was 2,133 ± 107 RMB ($334 ± 17). The annual burden of patients with autism was 86,700 ± 5,688 RMB ($13,596 ± 892). The estimated total annual burden of ASD was 5.548 billion RMB ($870 million) in Guizhou province.
Conclusion
The results revealed that rehabilitation resources are limited and that the burden of ASD is high in Guizhou province; therefore, improving the rehabilitation status and easing the burden of children with ASD is urgent in these regions.
Fruit spoilage and the production of ochratoxin A (OTA) by Aspergillus carbonarius are major causes of contamination of grape products. An OTA-producing strain of A. carbonarius 090614 was used to ...inoculate three grape cultivars, Thompson seedless, Kyoho, and Red Earth, via manual damage and non-damaging inoculations. Inoculated grape berries were incubated at 4, 25, and 30 °C, respectively. During the incubation, the diameter of rotten part of the berry, OTA accumulation, and reducing sugar content, soluble solids, total acidity, and pH were measured every day until the grape berries were completely rotted. No fungal colonization and OTA production were observed for all surface inoculated grape berries at all temperatures and in invasively inoculated grape berries incubated at 4 °C. Progression of the rotted area of the fruit and OTA accumulation were increased at 30 °C compared to 25 °C in all grape cultivars, and was the fastest for Thompson seedless, slow for Kyoho, and lowest for Red Earth berries. For all grape cultivars, reducing sugar content, soluble solids and pH decreased during cultivation, while total acidity content increased.
► Rot and OTA production were not observed for undamaged inoculated grapes. ► Incubation at 4 °C completely inhibited the rot and OTA production in grapes. ► Incubation at 30 °C promoted rot and OTA production more than 25 °C. ► Reducing sugar content decreased and then increased in damage inoculated grapes. ► Rot was fastest in Thompson seedless, slow in Kyoho and lowest in Red Earth.
The construction of deep foundation pits is characterized by heavy loads on pile foundations, complex interactions between the foundation pit and pile foundations, and stringent requirements for ...deformation control. In this work, FLAC3D was used to perform computational analyses on the displacement responses of pile caps and the retaining walls of foundation pits in a variety of cases and reinforcement schemes. The computational results indicate that the piles of skewed arches interact with the retaining walls of the foundation pits through soil masses. We also revealed the mechanism by which deep foundation pits interacted with the pile foundations of adjacent skewed arches. Based on the mechanisms of interaction between foundation pit excavations and the piles of skewed arches, we proposed three reinforcement schemes for controlling the deformations associated with these interactions. The arched wall reinforcement scheme could provide a satisfactory result in terms of the control of horizontal displacements in the pile foundations and project costs.
PDF
