Fluid-structure interaction of a wind turbine blade employing a refined finite element model coupled with a blade-element momentum method

Typically the aero-elastic simulation tools that are used in industry employ simple beam models to represent the blades of a wind turbine. The aerodynamic loads are usually calculated using a fast blade-element momentum (BEM) method. These models allow relatively fast calculation of the aero-elastic behavior of the blade which is required in order to allow the simulation of a large number of load cases as required by the IEC 61400 [1] and GL [2] standards in a feasible amount of time. Such beam models do however not incorporate the level of detail required to provide the complete stress and strain distribution in the blade, nor are they able to take into account nonlinear effects such as the change in cross-section of the blade due to the brazier effect [3]. Alternatively, highly detailed 3d computational fluid dynamics (CFD) simulations can be coupled with refined finite element (FE) models to obtain highly accurate results both regarding the flow around the blade as regarding the stress and strain distribution within the structure. However, the computational cost of such a simulation is enormous. In this work a coupling has been developed between the BEM code HAWC2-aero, which was developed by DTU [4] and the Abaqus FE solver. This allows a fluid-structure interaction (FSI) simulation by means of a so-called “weak” coupling, meaning that the two different solvers are run sequentially in iterations until convergence is achieved. In this way, a refined structural model is coupled with a fast aerodynamics tool, allowing steady-state fluid-structure interaction (FSI) simulations at an acceptable computational cost. The more advanced structural model allows the investigation of the influence of structural properties such as individual composite plies as well as their positioning, orientation and materials on the aero-elastic behavior of the blade. The influence of non-linear effects on the blade’s aero-elastic behavior can also be analyzed. The finite element model is used to locate stress hot-spots or buckling effects. Loads were applied using two different methods. One method uses distributing couplings to spread the load of a spanwise cross-section over all the nodes on that section. The other method uses concentrated forces at specific nodes to introduce the loads

Posing as Labour: Resisting The Anxious Condition of Post-Fordism in European Film Narratives by Dardenne, Loach, Petzold and Seidl

   In an interview, filmmaker Christian Petzold highlights that post-Fordism not only changed economic activity but also the affective balance. Hope and optimism linked to future prospects appear as outdated sentimental attributes that do not match the transition in affect (Brian Massumi) people go through living on the threshold between inclusion and exclusion. Film makers such as Luc and Jean-Pierre Dardenne (La Promesse, 1996), Ken Loach (It’s a Free World..., 2007), Christian Petzold (Jerichow, 2007), and Ulrich Seidl (Import Export, 2008) do not take the characters’ struggle for social recognition and economic persistence through labour as a given. In their films, the fight for survival is no longer tied to a redeemable promise of happiness; instead, it is triggered by an immediate affective impulse within a perpetual state of anxiety. Only elusive, globally preformatted consumer events prove to be stable. Posing (Petzold) becomes the actual skill exercised here. Participating in this diminished realm of everyday life has a significant impact on interpersonal and, consequently, on employment dynamics. This paper will show, through plot analysis, how European cinema aesthetically captures this instable affective condition. The films depict the emergence of both violence and ethics from this situation, emphasising the protagonists’ resilience against all odds within an adverse environment dominated by anxiety.&nbsp

The concept of segmented wind turbine blades : a review

There is a trend to increase the length of wind turbine blades in an effort to reduce the cost of energy (COE). This causes manufacturing and transportation issues, which have given rise to the concept of segmented wind turbine blades. In this concept, multiple segments can be transported separately. While this idea is not new, it has recently gained renewed interest. In this review paper, the concept of wind turbine blade segmentation and related literature is discussed. The motivation for dividing blades into segments is explained, and the cost of energy is considered to obtain requirements for such blades. An overview of possible implementations is provided, considering the split location and orientation, as well as the type of joint to be used. Many implementations draw from experience with similar joints such as the joint at the blade root, hub and root extenders and joints used in rotor tips and glider wings. Adhesive bonds are expected to provide structural and economic efficiency, but in-field assembly poses a big issue. Prototype segmented blades using T-bolt joints, studs and spar bridge concepts have proven successful, as well as aerodynamically-shaped root and hub extenders

External validation of a risk stratification model to assist shared decision making for patients starting renal replacement therapy

BACKGROUND: Shared decision making is nowadays acknowledged as an essential step when deciding on starting renal replacement therapy. Valid risk stratification of prognosis is, besides discussing quality of life, crucial in this regard. We intended to validate a recently published risk stratification model in a large cohort of incident patients starting renal replacement therapy in Flanders. METHODS: During 3 years (2001-2003), the data set collected for the Nederlandstalige Belgische Vereniging voor Nefrologie (NBVN) registry was expanded with parameters of comorbidity. For all incident patients, the abbreviated REIN score(aREIN), being the REIN score without the parameter "mobility", was calculated, and prognostication of mortality at 3, 6 and 12 month after start of renal replacement therapy (RRT) was evaluated. RESULTS: Three thousand four hundred seventy-two patients started RRT in Flanders during the observation period (mean age 67.6 ± 14.3, 56.7 % men, 33.6 % diabetes). The mean aREIN score was 4.1 ± 2.8, and 56.8, 23.1, 12.6 and 7.4 % of patients had a score of ≤4, 5-6, 7-8 or ≥9 respectively. Mortality at 3, 6 and 12 months was 8.6, 14.1 and 19.6 % in the overall and 13.2, 21.5 and 31.9 % in the group with age >75 respectively. In RoC analysis, the aREIN score had an AUC of 0.74 for prediction of survival at 3, 6 and 12 months. There was an incremental increase in mortality with the aREIN score from 5.6 to 45.8 % mortality at 6 months for those with a score ≤4 or ≥9 respectively. CONCLUSION: The aREIN score is a useful tool to predict short term prognosis of patients starting renal replacement therapy as based on comorbidity and age, and delivers meaningful discrimination between low and high risk populations. As such, it can be a useful instrument to be incorporated in shared decision making on whether or not start of dialysis is worthwhile

Supersymmetry with Dark Matter is still natural

We identify the parameter regions of the phenomenological minimal supersymmetric standard model (pMSSM) with the minimal possible fine-tuning. We show that the fine-tuning of the pMSSM is not large, nor under pressure by LHC searches. Low sbottom, stop and gluino masses turn out to be less relevant for low fine-tuning than commonly assumed. We show a link between low fine-tuning and the dark matter relic density. Fine-tuning arguments point to models with a dark matter candidate yielding the correct dark matter relic density: a bino-higgsino particle with a mass of $35-155$ GeV. Some of these candidates are compatible with recent hints seen in astrophysics experiments such as Fermi-LAT and AMS-02. We argue that upcoming direct search experiments, such as XENON1T, will test all of the most natural solutions in the next few years due to the sensitivity of these experiments on the spin-dependent WIMP-nucleon cross section.Comment: 8 pages, 5 figures, published versio

Bacterial diversity assessment in Antarctic terrestrial and aquatic microbial mats : a comparison between bidirectional pyrosequencing and cultivation

The application of high-throughput sequencing of the 16S rRNA gene has increased the size of microbial diversity datasets by several orders of magnitude, providing improved access to the rare biosphere compared with cultivation-based approaches and more established cultivation-independent techniques. By contrast, cultivation-based approaches allow the retrieval of both common and uncommon bacteria that can grow in the conditions used and provide access to strains for biotechnological applications. We performed bidirectional pyrosequencing of the bacterial 16S rRNA gene diversity in two terrestrial and seven aquatic Antarctic microbial mat samples previously studied by heterotrophic cultivation. While, not unexpectedly, 77.5% of genera recovered by pyrosequencing were not among the isolates, 25.6% of the genera picked up by cultivation were not detected by pyrosequencing. To allow comparison between both techniques, we focused on the five phyla (Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Deinococcus-Thermus) recovered by heterotrophic cultivation. Four of these phyla were among the most abundantly recovered by pyrosequencing. Strikingly, there was relatively little overlap between cultivation and the forward and reverse pyrosequencing-based datasets at the genus (17.1–22.2%) and OTU (3.5–3.6%) level (defined on a 97% similarity cut-off level). Comparison of the V1–V2 and V3–V2 datasets of the 16S rRNA gene revealed remarkable differences in number of OTUs and genera recovered. The forward dataset missed 33% of the genera from the reverse dataset despite comprising 50% more OTUs, while the reverse dataset did not contain 40% of the genera of the forward dataset. Similar observations were evident when comparing the forward and reverse cultivation datasets. Our results indicate that the region under consideration can have a large impact on perceived diversity, and should be considered when comparing different datasets. Finally, a high number of OTUs could not be classified using the RDP reference database, suggesting the presence of a large amount of novel diversity