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Near-wake effects of wind turbine models using the free-vortex wake have been studied extensively, but there is a lack of validation for such predictions in the mid to far wake. This paper presents a novel validation study using three free-vortex wake models of increasing complexity: an actuator disc, an actuator disc with rotation, and a lifting-line model. We emphasise the application for dynamic wind farm flow control optimisation with a focus on wake redirection using yaw misalignment. For this purpose, wake models should provide sufficiently accurate power predictions at a low computational expense to enable real-time control optimisation. Three sets of wind tunnel data are used for validation: flow measurements under steady yaw misalignment, time-resolved flow measurements for a step change in yaw, and turbine output measurements with yaw control and simulated wind direction variation. Results indicate that the actuator-disc model provides the best balance between computational cost and accuracy in power predictions for the mid to far wake, which is not significantly improved upon by the addition of rotation. In the near wake, the added complexity of the lifting-line model may provide value as it models blade loading and individual tip vortices. Altogether, this study provides important validation for further studies into optimisation of wake steering under time-varying conditions and suggests that the actuator-disc model is a suitable candidate for use in a model-predictive wind farm flow control framework.

Contains fulltext : 234416.pdf (Publisher’s version ) (Open Access) Contains fulltext : 234418.pdf (Publisher’s version ) (Open Access)

De Nederlandse samenleving gebruikt verschillende goederen en diensten die worden geleverd door ecosystemen. Alhoewel Nederlandse ecosystemen een belangrijke bijdrage leveren aan de behoefte aan een duurzame voorziening van goederen en diensten, voorzien ze niet in de totale vraag. Voor de meeste ecosysteemdiensten neemt de vraag ernaar sneller toe dan het aanbod in de afgelopen twintig jaar.

Latella, C, Teo, W-P, Spathis, J, and van den Hoek, D. Long-term strength adaptation: A 15-year analysis of powerlifting athletes. J Strength Cond Res 34(9): 2412-2418, 2020-Strength is a fundamental component of athletic performance and development. This investigation examined the long-term strength development of powerlifting (PL) athletes. The rate of strength gain/day was assessed in 1897 PL athletes (F 5 626, M 5 1,271) over a 15-year period (2003-2018). Independent T-tests explored sex differences in baseline absolute (kg) and relative strength (kg·body mass21 [bm]) recorded from the first competition, and strength gain/day (kg·d21). Analyses based on initial strength quartiles were conducted using one-way analysis of variances with significance set at p, 0.05. Bivariate correlational analysis tested for relationships between strength gain/day and baseline strength, the number of competitions, and mean days between competitions. Males had greater absolute (M: 513.3 6 99.8 kg, F: 289.4 6 55.7 kg, p, 0.001) and relative (M: 5.89 6 1.04 kg·bm21, F: 4.27 6 0.85 kg·bm21, p, 0.001) strength at baseline. Overall, strength gain/day (F: 0.12 6 0.69 kg·d21, M: 0.15 6 0.44 kg·d21, p 5 0.318) was similar between sexes. However, the strongest males showed a lower rate of strength improvement (0.102 kg·d21) compared with least strong males (0.211 kg·d21), p 5 0.010. No differences were observed across quartiles for females. Correlational analyses revealed significant but weak negative relationships between strength gain/day and the mean days between competitions for females (r2 5 20.120, p 5 0.003) and males (r2 5 2 0.190, p, 0.001). Similar relationships were observed for baseline strength (r2 5 20.073, p 5 0.009) and the number of competitions (r2 5 20.111, p, 0.001) for males. The results suggest similar strength adaptation between sexes. The strongest males improve more slowly, possibly due to a ceiling effect. Col

Het PBL heeft op verzoek van het ministerie van LNV een globale raming gemaakt van het potentieel effect van een extra pakket aan natuurmaatregelen van 300 miljoen euro/jaar tot en met 2030. Gevraagd is de effecten op de condities voor een gunstige staat van instandhouding van soorten van de Europese Vogel- en Habitatrichtlijnen (VHR) in beeld te brengen. Inschatting is dat met het extra pakket een winst te boeken is van grofweg 5-7 procentpunten aan doelbereik boven op het basispad. Het is een aanzienlijke extra stap op het vastgestelde beleid in het Natuurpact. Het pakket kan daarmee bijdragen aan het door de Raad van State nodig geachte ‘geloofwaardig en effectief pakket aan maatregelen om de instandhoudingsdoelstellingen voor de betrokken gebieden daadwerkelijk te bereiken’.

The Delta Works, a series of dams and barriers constructed in the 1960's–1980's changed the estuarine landscape of the Rhine-Meuse-Scheldt delta (SW Netherlands) into more stagnant and disengaged freshwater, brackish water or saltwater lakes. The remaining tidal systems were adapted by building a storm surge barrier in the Oosterschelde and dike reinforcement works along the Westerschelde. The Delta Works brought protection against flooding, but at the same time resulted in environmental and socio-economic problems, such as degradation of ecological quality and ecosystem functioning, disruption of fish migration routes, water and sediment quality problems.In this study we explore in an integrated, quantitative way the consequences of a number of management options for the Southwest Delta and their implications for the occurrence and distribution of aquatic and estuarine habitats, considering the mutual coherence between the water basins. Five scenarios were evaluated using a 1D hydraulic, water quality and primary production numerical model and GIS habitat mapping. Scenarios vary from small-scale interventions, such as changes in day-to-day management of hydraulic infrastructures or creation of small inlets in dams, feasible in the short term, to restoration of an open delta by removing dams and barriers, as a long term potential. We evaluate the outcomes in relation to the restoration of estuarine dynamics, as this is in policy plans proposed as a generic solution for the current ecological and environmental problems. Net water flow rates show more complex patterns when connectivity between water basins is increased and when sluice management is less strict. Estuarine transition zones and fish migration routes are partly restored, but only fully develop when basins are in open connection with each other. Area of intertidal habitats, tidal flats and tidal marshes, increases in each scenario, ranging between 7 and 83%, 1–56%, and 8–100% respectively, depending on sce

Contains fulltext : 125614.pdf (publisher's version ) (Open Access), BACKGROUND: Children in rural areas experience the interrelated problems of poor growth, anemia and parasitic infections. We investigated the prevalence of and associations between intestinal helminth and protozoan infections, malnutrition and anemia in school-age Venezuelan children. METHODS: This cross-sectional study was conducted in 390 children aged 4-16 years from three rural areas of Venezuela: the Amazon Region, Orinoco Delta and Carabobo State. Stool samples were collected for direct parasitic examinations. Anthropometric indicators of chronic (height-for-age Z score) and acute (weight-for-height and Body Mass Index (BMI)-for-age Z score in respectively children under 5 years of age and children aged 5 years and above) malnutrition were calculated. Multivariate linear and logistic regression models were built to determine factors associated with nutritional status and polyparasitism. RESULTS: Hookworm and Strongyloides stercoralis prevalences were highest in children from the Amazon rainforest (respectively 72% and 18%) while children from the Orinoco Delta and Carabobo State showed higher rates of Ascaris lumbricoides (respectively 28% and 37%) and Trichuris trichiura (40% in both regions). The prevalence of Giardia lamblia infection was not significantly different between regions (average: 18%). Anemia prevalence was highest in the Amazon Region (24%). Hemoglobin levels were significantly decreased in children with a hookworm infection. Malnutrition was present in respectively 84%, 30% and 13% of children from the Amazon Region, Orinoco Delta and Carabobo State. In multivariate analysis including all regions, G. lamblia and helminth infections were significantly and negatively associated with respectively height-for-age and weight-for-height/BMI-for-age Z scores. Furthermore, hemoglobin levels were positively associated with the height-for-age Z score (0.11, 95% CI 0.02 - 0.20). CONCLUSIONS: In rural populations in Venezuela helminthiasis and giardiasis w

A measurement of the final state distribution of the 8B beta decay, obtained by implanting a 8B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jyvaskyla [O. S.Kirsebom et al., Phys. Rev. C 83, 065802 (2011)]. It shows discrepancies with previously measuredspectra, leading to differences in the derived neutrino spectrum. Thanks to a low detection threshold, theneutrino spectrum is for the first time directly extracted from the measured final state distribution, thusavoiding the uncertainties related to the extrapolation of R-matrix fits. Combined with the IGISOL data,this leads to an improvement of the overall errors and the extension of the neutrino spectrum at highenergy. The new unperturbed neutrino spectrum represents a benchmark for future measurements of thesolar neutrino flux as a function of energy.

De Provincie Overijssel heeft een grondwaterkwaliteitsmeetnet, waarmee ze de toestand en de ontwikkeling van de grondwaterkwaliteit volgt. Op basis van metingen tussen 1993 en 2008 voerde Witteveen+Bos een evaluatie uit. Hoewel de landbouw de kwaliteit van het ondiepe grondwater nog sterk beïnvloedt - waardoor lokaal sprake is van overschrijding van normen - zet de al in 2004 ingezette verbetering door. Dit blijkt onder meer uit de uitgevoerde trendanalyse: voor de trends die afgeleid zijn, valt in het algemeen op dat voor de ondiepe filters gesteld kan worden dat het aantal filters met een dalende trend veel groter is dan het aantal filters met een stijgende. Een belangrijk aandachtspunt blijft echter de vorming van omzettingsproducten (bijvoorbeeld als gevolg van pyrietoxidatie), die tot op grote diepten aangetroffen worden.

Tot halverwege de vorige eeuw kwamen dotterbloemhooilanden veelvuldig voor, in de benedenlopen van beekdalen en het veengebied. Vanwege de rijke flora en fauna streven veel beheerders er naar ze terug te krijgen. Dit infoblad bekijkt de omstandigheden waaronder het mogelijk is dotterbloemhooilanden terug te krijgen en de mogelijke stimulerende maatregelen.

Een warmer en griliger klimaat zal via de waterhuishouding doorwerken op de natuur van Nederland. In een verkennende studie zijn de gevolgen voor binnendijkse ecosystemen in kaart gebracht. Verschillende ecosystemen, zoals hoogvenen en vennen, kunnen in de problemen komen, maar er zijn ook ecosystemen, zoals sprengbeken en droge duinen, die mogelijk profiteren van hogere temperaturen en soms meer neerslag, soms langdurige droogte. De uitkomsten zijn echter hoogst onzeker. Dat komt zowel door een aantal fundamentele tekortkomingen in de huidige generatie hydrologische modellen, als door een gebrek aan kennis over de sturende ecohydrologische processen. Nieuw onderzoek moet soelaas bieden