An optimized airfoil geometry for vertical-axis wind turbine applications

ABSTRACT

In this work, a new airfoil shape optimized for vertical-axis wind turbine applications is proposed. Different airfoil shapes have been analyzed with JavaFoil, a panel method software. Then, the results from the analysis have been used to optimize the performance of the new airfoil shape. Afterward, Computational Fluid Dynamics (CFD) simulations of the proposed airfoil, UO-17-LDA, are run for different angles of attack to provide insight into the flow field and the mechanisms related to this increase in performance. The UO-17-LDA airfoil presents a high lift-to-drag ratio and a delayed stall angle with respect to the original FX-63-137 airfoil, making it suitable for vertical-axis wind turbine applications. This increase in performance has been verified by comparing two VAWT designs with the original and the proposed airfoil using a double-multiple streamtube model. Finally, the practicality of JavaFoil for the comparison of different airfoil geometries has been verified, as it is capable of obtaining results for a wide number of flow conditions in small computational times and with a user-friendly interface. Nevertheless, the results diverge from the actual solution for high angles of attack (beyond stall). Hence, the time and effort required to perform CFD simulations is justified to gain insight into the actual behavior of a particular airfoil, as well as to obtain a richer analysis of the flow field and the mechanisms related to the airfoil performance.     

Economic and employment impacts of offshore wind for Ireland: A value chain analysis

ABSTRACT

The imminent development of a number of offshore wind farms in the Republic of Ireland presents a sizable opportunity to stimulate the Irish economy through the growth of an indigenous and globally competitive offshore wind supply chain. This study uses a value chain analysis to evaluate the economic and employment potential of the offshore wind sector for Ireland. The analysis is based on the expenditure on products and services required to develop an offshore wind farm, the planned capacity of projects in the pipeline, and the ability of Irish companies to supply the sector. Results suggest that by 2030, 2.5–4.5GW of domestic offshore wind development could create between 11,424 and 20,563 supply chain jobs and generate between €763 m and €1.4bn in gross value added. This is the first study to estimate domestic GVA potential for the sector.     

AN INSULATED EVAPORIMETER1

Evaporation was measured from a circular evaporation pan, 18 inches in diameter and 8 inches deep. The pan was insulated on the sides and bottom using 2 inches of freon-blown polyurethane foam. A U.S. Weather Bureau Class A evaporation pan was used to obtain reference evaporation measurements. Water evaporation from the Class A pan and the insulated pan were highly correlated. Using a water-methanol mixture, the insulated pan may be operated at temperatures below 32 F; the equivalent liquid water evaporation may be determined using a regression equation.     

A SEDIMENT RESUSPENSION AND WATER QUALITY MODEL OF LAKE OKEECHOBEE1

ABSTRACT: The influence of sediment resuspension on the water quality of shallow lakes is well documented. However, a search of the literature reveals no deterministic mass-balance eutrophication models that explicitly include resuspension. We modified the Lake Okeechobee water quality model - which uses the Water Analysis Simulation Package (WASP) to simulate algal dynamics and phosphorus, nitrogen, and oxygen cycles - to include inorganic suspend. ed solids and algorithms that: (1) define changes in depth with changes in volume; (2) compute sediment resuspension based on bottom shear stress; (3) compute partition coefficients for ammonia and ortho-phosphorus to solids; and (4) relate light attenuation to solids concentrations. The model calibration and validation were successful with the exception of dissolved inorganic nitrogen species which did not correspond well to observed data in the validation phase. This could be attributed to an inaccurate formulation of algal nitrogen preference and/or the absence of nitrogen fixation in the model. The model correctly predicted that the lake is light-limited from resuspended solids, and algae are primarily nitrogen limited. The model simulation suggested that biological fluxes greatly exceed external loads of dissolved nutrients; and sediment-water interactions of organic nitrogen and phosphorus far exceed external loads. A sensitivity analysis demonstrated that parameters affecting resuspension, settling, sediment nutrient and solids concentrations, mineralization, algal productivity, and algal stoichiometry are factors requiring further study to improve our understanding of the Lake Okeechobee ecosystem.     

ENVIRONMENTAL FACTORS INFLUENCING SUSPENDED SOLIDS IN THE LOXAIIATCHEE ESTUARY,FLORIDA1

ABSTRACT: A study was initiated to examine the effects of wind speed, wind direction, freshwater inflow, and tide height on suspended solid concentration and distribution in the Loxahatchee estuary, Florida. Recent efforts to increase freshwater flows in this system raised concerns that suspended solid concentrations would increase as well, which might result in negative impacts for the estuary. The data indicated that total suspended solids (TSS) in the estuary are derived primarily from the inlet and not from freshwater tributaries. In addition, total suspended solids and volatile suspended solids were correlated strongly with salinity, suggesting that suspended sediments act conservatively throughout this system. No one environmental factor had an overwhelming influence on suspended solid concentration throughout the estuary; different regions of the estuary were influenced by different factors. Freshwater inflow was negatively related to TSS in the upper reaches of the estuary but was positively related to TSS in the central embayment region of the estuary. We attribute this latter finding to the fact that extremely high inflows both prevented the normal transport upstream of tidal borne suspended sediments and promoted mixing when the freshwater front moving downstream confronted the tidal front moving upstream. Wind speed, wind direction, and tide height had relatively small effects on TSS concentration but were most influential in reaches upstream of the central embayment, where tidal velocity begins to diminish.     

An integrated modelling approach to assess the risk of wind-borne spread of foot-and-mouth disease virus from infected premises

Foot-and-mouth disease (FMD) is a highly contagious disease of livestock that has serious consequences on livestock production and trade. In Australia, preparedness and planning includes the development of decision-support tools that would assist priority setting and resource management in the event of an incursion. In this paper we describe an integrated modelling approach using geographic information system (GIS) technology to assess the risk of wind-borne spread of FMD virus. The approach involves linking an intra-farm virus production model, a wind transport and dispersal model, and an exposure-risk model to identify and rank farms at risk of wind-borne infection of FMD. This will assist authorities by enabling resources for activities like surveillance and vaccination to be allocated on the basis of risk.     

流场状态对渡槽槽体结构风载体形系数的影响

对矩形和U形渡槽槽体在均匀流场和湍流场中各取不同的高宽比进行了风洞试验,分别测量了槽内有水和无水两种情况下槽体各个部位的风压系数,进而算得了渡槽结构的风载体型系数.试验结果表明,湍流对渡槽槽体结构风载体形系数有显著影响,研究成果可为渡槽结构的抗风设计提供参考依据.     

超高层建筑风致响应中的数据挖掘

超高层建筑的风致响应问题已经越来越受到人们的重视.应用数据挖掘技术对广州中信广场大厦的实测数据进行了分析,并对该原型实测风致响应中的时间序列数据进行了相似性挖掘,发现了一些特征和规律,对该问题的进一步研究具有一定的参考价值.     

长江南通段江面风的观测分析

通过在长江南通段江面、江岸建立风观测站,并在江岸建设80m高的风梯度观测塔,与邻近气象站开展了较长时间的风同步观测,获得了实地观测数据.利用同步风观测数据进行对比分析,揭示出长江南通段江面风的观测事实,并利用风梯度观测资料,分析给出了风随高度的变化规律.在此基础上,结合邻近气象站长年的风观测资料,推算了该处的设计基本风速及其他工程设计风参数.分析表明,该处江面风况明显有别于邻近气象站,风参数计算结果也明显高于风工程理论推算值.     

建筑风载数值模拟的影响因素

通过对建筑物周围风场的计算流体动力学(CFD)模拟计算与原型试验结果的比较,分析了在应用CFD计算时应该考虑的计算区域、进口边界条件、湍流模型和网格划分等各种相关因素对CFD数值模拟结果准确度的影响.结果表明,在各种影响因素中,计算区域影响相对较小,而进口边界条件、网格划分和湍流模型的影响相对较大;而且进口边界条件中速度分布对计算结果的影响大于湍流强度分布对计算结果的影响,是进口边界条件中的关键部分.同时,根据上述比较,建议在网格划分中,对几何外形简单的单个建筑的数值模拟计算,优先采用结构化网格划分方法;对于湍流模型的选择,一般的工程应用中,建议在初步设计阶段选择RNGκ-ε湍流模型,而在最终设计阶段采用雷诺应力模型.