Search

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