Showing papers in "Wind Engineering in 2004"
TL;DR: In this article, the authors investigated the market penetration and share of different wind turbine concepts during the years 1998-2002, a period when the increase in the wind power capacity is starting to mark an abrupt evolution (more than two GW per year).
Abstract: The main aim of this paper is to investigate the market penetration and share of different wind turbine concepts during the years 1998-2002, a period when the increase in the wind power capacity is starting to mark an abrupt evolution (more than two GW per year). A detailed overview is performed based on suppliers market data and concept evaluation for each individual wind turbine type sold by the Top Ten suppliers over the selected five years. The investigation is processing information on a total number of approximately 90 wind turbine types from 13 different manufacturers, which have been on the Top Ten list of wind turbine suppliers during 1998 to 2002. The analysis is based on very comprehensive data, which cover approximately 76% of the accumulated world wind power installed at the end of 2002. The paper also provides an overall perspective on the contemporary wind turbine concepts, classified with respect to both their speed control ability and to their power control type. Trends for wind turbine c...
211 citations
TL;DR: In this paper, an overall control method for variable speed pitch controlled wind turbines with doubly-fed induction generators (DFIGs) is presented, focusing on control strategies and algorithms applied at each hierarchical control level of the wind turbine.
Abstract: The paper presents an overall control method for variable speed pitch controlled wind turbines with doubly-fed induction generators (DFIG). Emphasis is on control strategies and algorithms applied at each hierarchical control level of the wind turbine. The objectives of the control system are: 1) to control the power drawn from the wind turbine in order to track the wind turbine maximum power operation point, 2) to limit the power in case of large wind speeds, and 3) to control the reactive power interchanged between the wind turbine generator and the grid. The present control method is designed for normal continuous operations. The strongest feature of the implemented control method is that it allows the turbine to operate with the optimum power efficiency over a wider range of wind speeds. The model of the variable speed, variable pitch wind turbine with doubly-fed induction generator is implemented in the dynamic power system simulation tool DIgSILENT PowerFactory which allows investigation of the dyna...
179 citations
TL;DR: In this article, the authors explored possible cost reductions until 2020 for each of the initial investment costs of offshore wind farms, which mainly consist of the wind turbines, foundations, internal and external grid-connections and installation.
Abstract: The economics of offshore wind farms are presently less favorable than for onshore wind energy. Consequently there is a strong need for significant cost reductions in order to become competitive. About 70% of the electricity cost of offshore wind farms is determined by the initial investment costs, which mainly consist of the wind turbines, foundations, internal and external grid-connections and installation. Possible cost reductions until 2020 are explored for each of these components. Technological developments and cost reduction trends in both the offshore and onshore wind sector are analyzed. Information is also taken from offshore oil and gas sector and from the experience with high-voltage submarine transmission of electricity. Where possible, cost reduction trends are quantified using the experience curve concept, or otherwise based on expert judgments. Main drivers for cost reduction appear to be (a) design improvements and upscaling of wind turbines, (b) the continuing growth of onshore wind capa...
175 citations
TL;DR: In this article, the authors consider the computational design of blades for small wind turbines for the dual purposes of (i) efficient power production at rated wind speeds and (ii) rapid starting at smaller wind speeds.
Abstract: Experimental studies of the starting behaviour of small wind turbines have shown that the initial "idling period", characterised by small rotor acceleration, is usually much longer than the subsequent period of rapid accleration to reach operational rotor speed. Idling obviously reduces the power generation potential of any turbine. The experimental results also imply that most starting torque is generated near the hub, whereas power-producing torque is concentrated near the tip. Therefore this paper considers the computational design of blades for small wind turbines for the dual purposes of (i) efficient power production at rated wind speeds and (ii) rapid starting at smaller wind speeds. Standard blade element theory is used to determine the power coefficient, which is the first objective function to be maximised. A modified blade element method gives the start, whose inverse is the second objective function. During the idling period, the blade angles of attack are relatively large, allowing the lift a...
54 citations
TL;DR: In this paper, the ability of induction generator-based wind turbines to remain connected through power system disturbances is discussed, and a control loop for a 'fast pitching' blade angle control strategy to provide a power system fault ride-through capability for induction generator based wind turbines is also described.
Abstract: Until recently it has been accepted that induction generator based wind turbines are disconnected from the power system in the event of a network disturbance. However, the increasing trend of connecting high penetrations of wind farms to transmission networks has resulted in the transmission system operators revising their grid codes for the connection of large MW capacity wind farms. These documents now require wind turbines to remain connected for a specified voltage disturbance on the network. Much of the wind generation plant being developed will use either fixed speed induction generator (FSIG) or doubly fed induction generator (DFIG) based wind turbines. The ability of induction generator based wind turbines to remain connected through power system disturbances is discussed. A control loop for a 'fast pitching' blade angle control strategy to provide a power system fault ride-through capability for induction generator based wind turbines is also described. A case study of a FSIG wind turbine with th...
48 citations
TL;DR: In this article, the importance of a short-term wind power-prediction tool for the participation of wind energy systems in electricity markets is studied, and it is concluded that income from participation in the electricity markets can be increased using a short term wind power prediction tool of average accuracy.
Abstract: One of the characteristics of wind energy, from the grid point of view, is its non-dispatchability, i.e. generation cannot be ordered, hence integration in electrical networks may be difficult. Short-term wind power prediction-tools could make this integration easier, either by their use by the grid System Operator, or by promoting the participation of wind farms in the electricity markets and using prediction tools to make their bids in the market. In this paper, the importance of a short-term wind power-prediction tool for the participation of wind energy systems in electricity markets is studied. Simulations, according to the current Spanish market rules, have been performed to the production of different wind farms, with different degrees of accuracy in the prediction tool. It may be concluded that income from participation in electricity markets is increased using a short-term wind power prediction-tool of average accuracy. This both marginally increases income and also reduces the impact on system o...
44 citations
TL;DR: In this article, the effects of increased Reynolds number (Re) on clean and rough airfoils were investigated by wind tunnel experiments and by numerical simulation with an improved Navier-Stokes solver.
Abstract: The effects of increased Reynolds number (Re) on clean and rough airfoils were investigated by wind tunnel experiments and by numerical simulation with an improved Navier-Stokes solver. By cooling the cryogenic wind tunnel in Cologne (KKK) of the German-Dutch Wind-Tunnel (DNW) down to 100 K, values of Re up to 10 × 106 were reached, based on a model chord of 500 mm. Whereas the clean surface configuration shows no drastic loss in maximum lift, the lift-to-drag ratio decreases from 95 to approximately 85, mainly due to an increase of drag. In contrast to that, rough surface configurations, including zig-zag tape for transition fixing and carborundum based distributed roughness around the nose, show increased performance for increased Re. In parallel, numerical simulations were carried out with a boundary layer stability code coupled to a Navier-Stokes solver. The trends in behaviour of the boundary-layer based properties were predicted well, in contrast to the separation pattern responsible for maximum lift.
43 citations
TL;DR: In this article, simulations on a large wind farm model consisting of eighty wind turbines, when subjected to a short-circuit fault, are presented, showing that the wind turbines show coherent response at the grid fault.
Abstract: One of the main concerns of grid-integration of large wind farms with variable-speed wind turbines equipped with doubly-fed induction generators controlled by back-to-back converters is a possible risk of mutual interaction between the control systems of the converters. This topic is discussed and illustrated by simulations on a large wind farm model consisting of eighty wind turbines, when subjected to a short-circuit fault. At no mutual interaction, the wind turbines show coherent response at the grid fault. In such a case, large wind farms can be represented by one-machine equivalent, e.g. one wind turbine model with re-scaled power capacity. This simplification can be applied for voltage stability investigations carried out on detailed models of large power systems.
42 citations
TL;DR: In this article, a new automatic method of calculation of a long-term representative wind climate is proposed, based on the calculation of the joint probability distribution of the wind at a local station and at a longterm reference meteorological mast.
Abstract: A new automatic method of calculation of a long-term representative wind climate is proposed. The procedure is based on the calculation of the joint probability distribution of the wind at a local station and at a long-term reference meteorological mast. The results obtained with this algorithm are compared with estimations of the long-term climate obtained with a Measure-Correlate-Predict method. The agreement found is good, even for very different periods of measurement.
36 citations
TL;DR: In this paper, an active-stall wind turbine controller is described for continuous operation under all wind speeds from start-up wind speed to shut down wind speed, which can represent different active stall wind turbine controllers and can be implemented in different simulation tools.
Abstract: This paper describes an active-stall wind turbine controller. The objective is to develop a general model of an active stall controller in order to simulate the operation of grid connected active stall wind turbines. The active stall turbine concept and its control strategies are presented and evaluated by simulations. The presented controller is described for continuous operation under all wind speeds from start-up wind speed to shut down wind speed. Due to its parametric implementation it is general i.e. it can represent different active stall wind turbine controllers and can be implemented in different simulation tools.
35 citations
TL;DR: In this article, the basic principles for establishing a simulation-model of a variable speed, pitch regulated, wind turbine are considered and a detailed and didactic analysis of the interaction between wind and turbine is given.
Abstract: This paper considers the basic principles for establishing a simulation-model of a variable speed, pitch regulated, wind turbine. This model is used to test various control algorithms designed with the aim of maximising energetic yield and robustness and minimising flicker emission and dynamic drive train loads. One of the most complex elements of such a system is the interaction between wind and turbine. First, a detailed and didactic analysis of this interaction is given. This is used to understand some complicated phenomena, and to help design a simpler and more efficient (in terms of processing time) mathematical model. Additional submodels are given for the mechanical coupling, the pitch system and the electrical power system, before the entire model is validated by comparison with filed measurements on a 180 kW turbine. The complete simulation model is flexible, efficient and allows easy evaluation of different control algorithms.
TL;DR: In this paper, the effects of rotating rotor blades on the nacelle anemometry of a horizontal axis wind turbine (HAWT) were investigated using the Reynolds averaged Navier-Stokes equations.
Abstract: The objective of this paper is to study the typical atmospheric turbulent flow around the rotor and nacelle of a HAWT, in order to (i) investigate the impact of the turbine's rotating blades on the flow field over the nacelle, i.e. the rotor-nacelle interaction; (ii) assess the appropriate anemometer location on the nacelle, and therefore (iii) establish the relationship between wind speed measured near the nacelle and free stream wind speed. The paper presents a numerical method for investigating the effects of rotating rotor blades on the nacelle anemometry of a horizontal axis wind turbine (HAWT). The flow field around the turbine and nacelle is described by the Reynolds averaged Navier-Stokes equations. The κ – ϵ model has been chosen for the closure of time-averaged turbulent flow equations. The rotor is modelled using the actuator-disk concept. The simulation results were performed using a commercial wind turbine rated at 750kW. In general, good qualitative agreements have been found, supporting the...
TL;DR: In this article, hourly mean wind-speed data recorded at Rafha, Saudi Arabia, have been analyzed for the potential of utilising autonomous hybrid (wind-diesel) power systems to meet the load requirements of a typical remote settlement, namely Rawdhat Bin Habbas, near Rafha and with a population of 10,000 and having an annual electrical energy demand of 13,200 MWh.
Abstract: In the present study, hourly mean wind-speed data recorded at Rafha, Saudi Arabia, have been analyzed for the potential of utilising autonomous hybrid (wind-diesel) power systems to meet the load requirements of a typical remote settlement, namely Rawdhat Bin Habbas, near Rafha and with a population of 10,000 and having an annual electrical energy demand of 13,200 MWh. The monthly average wind speeds range from 2.7 m/s to 4.2 m/s at 10 m height. The hybrid systems considered consist of different combinations of 1.3 MW commercial wind machines supplemented with diesel generators. National Renewable Energy Laboratory's (NREL's) HOMER software has been used to evaluate the potential of hybrid wind-diesel power systems.The study indicates that for a hybrid system consisting of 3.9 MW (three 1.3 MW wind machines, 50 m hub-height) wind farm capacity together with 4.5 MW diesel system (three 1.5 MW units), the simulated wind penetration is 24%. The cost of electricity from this hybrid configuration is calculated...
TL;DR: In this paper, the effect of surface roughness by varying the roughness size and location on the aerodynamic characteristics of the airfoil was investigated and the results showed that as the surface smoothness increases, the minimum drag also increases due to the increase of the skin friction and the lift decreases.
Abstract: The objective of this study is to investigate the effect of surface roughness by varying the roughness size and location on the aerodynamic characteristics of the airfoil Tests were conducted on the symmetrical airfoil models NACA 0012 on which the nature of the surface was varied from smooth to very rough and at a chord Reynolds number of 15*105 Different airfoil models with various roughness sizes and roughness locations were tested for different angles of attack Lift, drag and pressure coefficients were measured and velocity profiles were determined for the smooth and grit 36 roughened modelsIt is shown that as the surface roughness increases, the minimum drag also increases due to the increase of the skin friction and the lift decreases Surface roughness is seen to delay the stall angle and also increase the lift in the stall regionThe airfoil model with the roughness located at the trailing edge shows minimum drag and maximum lift up to the stall angle compared to the other cases of different
TL;DR: In this article, the authors presented a new wind turbine simulator for steady state conditions, which consists of a 10 hp induction motor (IM), which drives a synchronous generator and is driven by a 10 kW variable speed drive inverter, and real time control software.
Abstract: This paper presents a new wind turbine simulator for steady state conditions. In order to provide a test platform for wind turbine drive trains, the authors have developed an experimental system to simulate the static characteristics of real wind turbines. This system consists of a 10 hp induction motor (IM), which drives a synchronous generator and is driven by a 10 kW variable-speed drive inverter, and real time control software. A microcontroller, a PC interfaced to a LAB Windows I/O board, and an IGBT inverter-controlled induction motor are used instead of a real wind turbine to supply shaft torque. A control program written in the C language is developed that obtains wind profiles and, by using turbine characteristics and the rotational speed of the IM, calculates the theoretical shaft torque of a real wind turbine. Based on the comparison of the measured torque with this demand torque, the shaft torque of the IM is regulated accordingly by controlling stator current demand and frequency demand of an...
TL;DR: In this article, the authors used a Weibull probability distribution function (PDF) to estimate the annual energy production (AEP) of a wind turbine in the region of La Ventosa in Mexico, where the frequency of wind speed shows a bimodal distribution.
Abstract: The International Standard IEC 61400-12 and other international recommendations suggest the use of the two-parameter Weibull probability distribution function (PDF) to estimate the Annual Energy Production (AEP) of a wind turbine. Most of the commercial software uses the unimodal Weibull PDF as the default option to carry out estimations of AEP, which in turn, are used to optimise wind farm layouts. Furthermore, AEP is essential data to assess the economic feasibility of a wind power project. However, in some regions of the world, the use of these widely adopted and recommended methods lead to incorrect results. This is the case for the region of La Ventosa in Mexico, where the frequency of the wind speed shows a bimodal distribution. In this work, mathematical formulations by using a Weibull PDF and a bimodal distribution are established to compare the AEP, the capacity factor and the levelised production cost for a specific wind turbine. By combining one year of wind speed data with the hypothetic power performance of the Vestas V27-225 kW wind turbine, it was found that using the Weibull PDF underestimates AEP (and thus the Capacity Factor) by about 12%.
TL;DR: In this paper, various approaches and challenges for the simulation of power system dynamics are discussed and the associated modelling is analysed, including the interaction of wind turbines with the power system, including their impact on its dynamic behaviour.
Abstract: Increasing amounts of wind turbines are connected to electrical power systems in order to mitigate the negative environmental consequences of conventional electricity generation. There are, however, fundamental differences between conventional and wind power generation, particularly regarding the controllability of the prime mover and the generator types used to convert mechanical energy into electricity. These differences relate to the interaction of wind turbines with the power system, including their impact on its dynamic behaviour. In order to investigate the impact of wind power on power system dynamics, adequate models are essential. However, generally accepted models for representing wind turbines in power-system dynamics simulations are presently not generally available. In this paper, various approaches and challenges for the simulation of power system dynamics are discussed and the associated modelling is analysed.
TL;DR: In this paper, the interaction between two horizontal axis wind turbines under two different flow patterns is investigated through wind tunnel tests, and the results include the effects of inflow velocity, turbulence intensity and turbine array on wind turbine output power as affected by the wake.
Abstract: Interactions between neighboring wind turbines in complex terrain are complex and many problems are still unsolved. This paper, through wind tunnel tests, investigates the interaction between two horizontal axis wind turbines (HAWTs) under two different flow patterns. The purpose of the study is to begin to obtain fundamental procedures for arranging turbines in a wind farm in a complex terrain, with no-fixed intervals between wind turbines and different wind conditions. The main factors investigated are: (1) experimental analysis of the wake behind HAWTs, (2) performance measurements of the HAWTs, and (3) detailed investigation of interaction between two HAWTs. The results include the effects of inflow velocity, turbulence intensity and turbine array on wind turbine output power as affected by the wake.
TL;DR: The status and perspectives of development of wind-powered desalination are reviewed in this article, where reverse osmosis (RO), mechanical vapour compression (MVC) and electrodialysis (ED) are discussed.
Abstract: Since energy requirements for desalination processes are large, the energy supply in remote areas is a problem, especially if electricity is required. The status and perspectives of development of wind-powered desalination are reviewed in this paper. Desalination processes suitable for coupling to wind turbines are reverse osmosis (RO), mechanical vapour compression (MVC) and electrodialysis (ED). Wind-powered RO is the most mature technology whereas there are very few pilot plants of wind-driving MVC and ED.
TL;DR: In this article, the authors explored technical and other issues arising from using shaped timber for a 1 metre long high efficiency blade for a small 600 W wind turbine and found that hoop pine is 25% stronger and 6% more fatigue resistant than radiata pine.
Abstract: This paper explores technical and other issues arising from using shaped timber for a 1 metre long high efficiency blade for a small 600 W wind turbine. Two readily available Australian grown softwood timber species, radiata pine and hoop pine, were selected. Reasons for selecting these timbers are detailed in the paper. The fatigue life of the both timbers was determined using four point flexural testing. Results show that hoop pine is 25% stronger and 6% more fatigue resistant than radiata pine. A fatigue test procedure for the 1 m blade has been created based on the aeroelastic response of a 2.5 m long composite wind turbine blade and wind data from the Australian Bureau of Meteorology. Blade fatigue-life predictions, using Miners rule for fatigue damage accumulation, indicated effectively unlimited fatigue-life for a blade constructed from hoop pine, with the turbine operating at design performance in wind speeds up to 20 m/s. The blade's life was reduced to a few months when it was constructed from r...
TL;DR: In this article, the authors assess the connection of a large wind farm to a regional power system with a weak link to the main transmission grid and demonstrate that utilization of modern wind turbine technology and automatic generation control schemes allow operation of large wind farms in weak grids.
Abstract: This paper assesses the connection of a large wind farm to a regional power system with a weak link to the main transmission grid. The study demonstrates that utilization of modern wind turbine technology and automatic generation control schemes allow operation of large wind farms in weak grids. In the case study considered of a regional power system, the viable wind farm capacity may be increased from 50 to 200 MW.
TL;DR: In this article, the authors report the results of technical and economic feasibility studies of floating offshore wind farms under typical environmental conditions in Japanese Waters, with economic assessments, both horizontal and vertical axis wind turbines are considered, although it is realised that horizontal axis machines now dominate.
Abstract: This paper reports the results of technical and economic feasibility studies of floating offshore wind farms under typical environmental conditions in Japanese Waters. Outline designs are considered, with economic assessments. Both horizontal and vertical axis wind turbines are considered, although it is realised that horizontal axis machines now dominate.
TL;DR: Based on experience from technical and market-oriented studies on offshore wind energy (OWE), the Energy research Centre of the Netherlands ECN concludes that the growth of OWE in the next few years will mainly be hampered by insufficient policy support, rather than by technical barriers as mentioned in this paper.
Abstract: With the ground breaking 160 megawatt wind farm Horns Rev, off the coast of Denmark in the North Sea, installed and operating, offshore wind energy experts are progressing with optimism. With a portfolio for offshore wind farms in north-western Europe that foresees in an accumulated installed power of more than 3 gigawatt by the end of 2006, the future indeed looks bright. But will the expectations for offshore wind energy be met? Based on experience from technical and market-orientated studies on offshore wind energy (OWE), the Energy research Centre of the Netherlands ECN concludes that the growth of OWE in the next few years will mainly be hampered by insufficient policy support, rather than by technical barriers. The realisation of the first two Dutch offshore wind farms has been delayed considerably. Towards the end of 2004, the Dutch policy will shift to a concession system for the issuing of exclusive rights for plots in the North Sea. For the tendered sites surrounding the UK coast, the financial ...
TL;DR: In this paper, the authors analyse the dynamic models for wind turbine generators available during 2003 to the Irish Transmission system operator, ESB National Grid, focusing on the modelling of Doubly-Fed Induction Generators (DFIGs).
Abstract: The penetration of wind energy into small, lightly interconnected power systems, as in Ireland, is increasing. It is therefore important to study how wind farms will interact dynamically with conventional generators and loads. For the future, we need to asses the impact this will have on the stability of the whole system. To investigate this interaction, dynamic simulation studies of the system, with the inclusion of wind turbine generators (WTGs), are important. This requires these generators to be represented in power-system simulation studies to at least the same detail as conventional machines. This paper analyses the dynamic models for WTGs available during 2003 to the Irish Transmission system operator, ESB National Grid. The paper focuses on the modelling of Doubly-Fed Induction Generators (DFIGs). A comparison of the models was carried out and the main conclusions drawn are discussed.
TL;DR: In this paper, the effect of the concentrator and its optimum design on the performance of wind rotors was analyzed and it was shown that power augmentation is increased if the position of the rotor is correctly behind the outlet of a concentrator, the outlet diameter is smaller than the rotor diameter, and the inlet diameter is much larger than rotor diameter.
Abstract: Various power augmentation systems have been studied to improve the performance of wind rotors by increasing the energy density of the wind. One of them is the ducted augmentation system. However, most of the studies of the ducted rotor concern the effect of the diffuser [1] [2] while little research has been done concerning the concentrator (nozzle). This paper analyses the effect of the concentrator and its optimum design. The effect of power augmentation is increased if (a) the position of the rotor is correctly behind the outlet of the concentrator, (b) the outlet diameter of the concentrator is smaller than the rotor diameter, and © the inlet diameter is much larger than the rotor diameter.
TL;DR: In this article, the state of the Irish electricity system at the end of 2003, describes the status of the electricity market and puts into perspective the technical issues which need to be resolved to increase wind penetration on the island of Ireland.
Abstract: Ireland is a facing a critical time in the formation of a robust renewable energy (RE) policy, due to its size, relative isolation, grid infrastructure, and fuel import dependency. The inherent intermittency and unpredictability of wind power make its increased penetration into the electricity network an area requiring significant further analysis. This paper details the state of the Irish electricity system at the end of 2003, describes the status of the electricity market and puts into perspective the technical issues which need to be resolved to increase wind penetration on the island of Ireland.
TL;DR: In this article, the authors summarise two reports that were commissioned to analyse impacts of increasing the wind power penetration on the island of Ireland, and assess the contribution renewable sources can make to the Northern Ireland electricity system.
Abstract: This paper summarises two reports that were commissioned to analyse impacts of increasing the wind power penetration on the Island of Ireland. The first report was commissioned by Northern Ireland Electricity (NIE) and assesses the contribution renewable sources can make to the Northern Ireland electricity system. The second report was commissioned by the Commission for Energy Regulation (CER) and the Office for the Regulation of Electricity and Gas (Ofreg); it examines the possible effects increasing wind generation would have on the combined systems of Northern Ireland and the Republic of Ireland. The reports undertake a detailed analysis of the potential wind resource available, and the likely impact it may have on the respective transmission and distribution systems. The possible effects that increased amounts of wind generation may have on the system operation are examined and various economic implications are assessed.
TL;DR: In this article, a model of a Static VAR Compensator (SVC) with dynamic generic control is presented, which is a kind of dynamic reactive compensation devices that is associated with reactive power and voltage control of induction generator based wind turbines.
Abstract: Dynamic reactive compensation is associated with reactive power and voltage control of induction generator based wind turbines. With regard to wind power, application areas of dynamic reactive compensation can be improvement of the power quality and the voltage stability, the control of the reactive power exchange between the wind farm and the power grid in the wind farm connection point as well as improvement of the ride-through capability of the wind farm. This article presents a model of a Static VAR Compensator (SVC) with dynamic generic control that is a kind of dynamic reactive compensation devices. The term "generic" implies that the model is general and must cover a variety of the SVC units and their specific controls from different manufacturers. The SVC model with dynamic generic control is implemented by Eltra in the simulation tool Powerfactory and validated from the SVC model in the tool PSCAD/EMTDC. Implementation in the tool Powerfactory makes it possible to apply the SVC model with dynamic...
TL;DR: In this paper, the benefits of using remote sensing methodology as an intermediate step to assess offshore and coastal wind resources are discussed, based on an ongoing research to understand wind patterns in the St-Lawrence Gulf.
Abstract: This paper illustrates the benefits of using remote sensing methodology as an intermediate step to assess offshore and coastal wind resources. Results are based on an ongoing research to understand wind patterns in the St-Lawrence Gulf. This area combines two advantages for wind power development in Canada: a) very good wind, b) high potential of the large scale integration of wind power with the hydro-wind concept. Advantages and drawbacks of satellite techniques in such a complex environment are reviewed. Our approach of satellite data selection for dominant wind conditions reduces the weakness of Synthetic Aperture Radar (SAR) satellite temporal resolution. Wind fields are extracted from sixteen scenes provided by RADARSAT-1. Results are compared with two main sources: in situ measurements and QuickSCAT scatterometer computations. Among interesting findings, it appears that a relative small sample of scenes can already indicates the best wind sites to be investigated for further analysis. The proposed ...
TL;DR: In this paper, a comparative study of combining turbulence models and interpolation schemes to calculate turbulent flow around a NACA0012 airfoil before and after separation was performed using CAFFA of Peric.
Abstract: This paper is a comparative study of combining turbulence models and interpolation schemes to calculate turbulent flow around a NACA0012 airfoil before and after separation. The calculations were carried out using the code CAFFA of Peric, which was appropriately modified to include more numerical schemes and turbulence models. This code solves the Navier-Stokes equations for 2D incompressible flow, using finite volumes and structured, collocated, curvilinear, body fitted grids. Seven differencing schemes were investigated: central, upwind, hybrid, QUICK, Harten-Yee upwind TVD with five limiters, Roe-Sweby upwind TVD with three limiters, and Davis-Yee symmetric TVD with three limiters. Turbulence effects were incorporated using four turbulence models: standard k-e, k-ω high Re with wall functions, k-ω high Re with integration up to the wall, and the k-ω low Re model. A parametric study showed that best results are obtained: a) for the k-e model, when using the Harten-Yee upwind TVD scheme for the velocities and the upwind interpolation for the turbulence properties k and e, and b) for the k-ω models, when using the Harten-Yee upwind TVD scheme with different limiters for the velocities and the turbulence quantities k and ω. The turbulence models that integrate up to the wall are more accurate when separation appears, while those using wall functions converge much faster.