Modelling wind turbine wakes for wind farms (original) (raw)
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Modeling Wind Turbine Wakes for Wind Farms
Lehr/Alternative, 2016
The simulation of the wakes behind wind turbines is important in predicting energy yields in wind farms, and so plays a role in planning the layout of these farms. As both wind turbines and farms increase in size, wind farm modellers have faced challenges as previously-held assumptions and parameterisations become inadequate-requiring more detailed, less parameterised methods such as those available through computational fluid dynamics. In this article the authors chart the progress of wind turbine wake modelling from analytical methods towards computational fluid dynamics, discussing approaches such as Reynolds-averaged Navier-Stokes and Large Eddy Simulation.
Survey of modelling methods for wind turbine wakes and wind farms
Wind Energy, 1999
This article provides an overview and analysis of different wake-modelling methods which may be used as prediction and design tools for both wind turbines and wind farms. We also survey the available data concerning the measurement of wind magnitudes in both single wakes and wind farms, and of loading effects on wind turbines under single-and multiple-wake conditions. The relative merits of existing wake and wind farm models and their ability to reproduce experimental results are discussed. Conclusions are provided concerning the usefulness of the different modelling approaches examined, and dif®cult issues which have not yet been satisfactorily treated and which require further research are discussed.
Computational Fluid Dynamic Models of Wind Turbine Wakes
Energies
Wind energy is one of the main sources of renewable energy that does not contaminate and contributes significantly to the reduction of burning fossil fuels that originate global warming by creating greenhouse gasses; therefore, a significant part the electric energy produced presently is of wind origin, and this share is expected to become more important in the next years [...]
Numerical Computations of Wind Turbine Wakes
Wind Energy, 2007
Numerical simulations of the Navier-Stokes equations are performed to achieve a better understanding of the behaviour of wakes generated by wind turbines. The simulations are performed by combining the in-house developed computer code EllipSys3D with the actuator line and disc methodologies. In the actuator line and disc methods the blades are represented by a line or a disc on which body forces representing the loading are introduced. The body forces are determined by computing local angles of attack and using tabulated aerofoil coefficients. The advantage of using the actuator disc technique is that it is not necessary to resolve blade boundary layers. Instead the computational resources are devoted to simulating the dynamics of the flow structures.
Modelling and measurements of wakes in large wind farms
Journal of Physics: Conference Series, 2007
The paper presents research conducted in the Flow workpackage of the EU funded UPWIND project which focuses on improving models of flow within and downwind of large wind farms in complex terrain and offshore. The main activity is modelling the behaviour of wind turbine wakes in order to improve power output predictions.
Wind Energy, 2012
Computational fluid dynamic (CFD) methods are used in this paper to predict the power production from entire wind farms in complex terrain and to shed some light into the wake flow patterns. Two full 3D Navier-Stokes solvers for incompressible fluid flow, employing k-ε and k-ω turbulence closures, are used. The wind turbines are modelled as momentum absorbers by means of their thrust coefficient through the actuator disk approach. Alternative methods for estimating the reference wind speed in the calculation of the thrust are tested. The work presented in this paper is part of the work being undertaken within the UpWind Integrated Project that aims to develop the design tools for next generation of large wind turbines. In this part of UpWind, the performance of wind farm and wake models is being examined in complex terrain environment where there are few pre-existing relevant measurements. The focus of the work carried out is to evaluate the performance of CFD models in large wind farm applications in complex terrain and to examine the development of the wakes in a complex terrain environment.
Modelling of wind turbine wake using large eddy simulation
Renewable Energy, 2018
In an array of wind turbines, the interaction of the downstream machines with the wakes from the upstream ones results in a reduction in the overall wind farm performance. Turbine wakes are a major source of turbulence which exerts fluctuating loads on the blades of the downstream turbines, resulting in the generation of noise and fatigue of the turbine blades. There are many semi-empirical wind turbine wake models in the literature. This paper, develops a fully numerical model of wind turbine wakes using CFD by means of a Large Eddy Simulation (LES). The new LES model is tested against experimental data, showing very good agreement. The advantages of the LES model compared to the available semi-empirical models in the literature are discussed and it is shown that the LES model is very accurate compared to the conventional semi-empirical wake models usually used in the industry. Moreover, the LES model is used as a benchmark to compare the accuracy of these semi-empirical models; it is shown that the model proposed by Jensen can predict the velocity deficit most accurately among the semi-empirical models, while the highest degree of accuracy in the wake expansion is achieved by using the Larsen model.
Flow and wakes in large offshore wind farms using a cfd approach
Power losses due to wind turbine wakes are of the order of 10 and 20% of total power output in large wind farms. The main objective of the present research work is to evaluate and improve a fully elliptic CFD approach to simulate wake effects in large offshore wind farms. This research is part of the EC funded UPWIND project which aims to radically improve wind turbine and wind farm models and further reduce the costs of wind energy. For this purpose a CFD model by the name 3D-NS has been developed. The model solves the 3D Reynolds averaged incompressible Navier-Stokes equations (RANS) on a staggered Cartesian grid using the k-ε turbulence closure model. The wind turbines are accommodated in its grid as momentum sinks. The focus has been on cases for the Danish offshore wind farm Horns Rev consisting of 80 wind turbines located in an 8 by 10 grid. Using the power curve, wind velocity field predictions are converted into power output which is compared with measurements. Although some...
Large-Eddy Simulation of wind turbines wakes including geometrical effects
Computers & Fluids, 2018
Accurate simulation of wind turbine wakes is critical for the optimization of turbine efficiency and prediction of fatigue loads. These wakes are three-dimensional, complex, unsteady and can evolve in geometrically complex environments. Modeling these flows calls thus for high-quality numerical methods that are able to capture and transport thin vortical structures on an unstructured grid. It is proposed here to assess the performances of a fourth-order finite-volume LES solver to perform massively parallel scale-resolving simulations of wind turbines wakes. In this framework, the actuator line method that takes the effect of the wind turbine blades on the flow into account is implemented. It is demonstrated that both near and far parts of the turbine wakes are accurately modeled as well as geometrical details. The methodology is assessed on two different test cases and validated with experimental results. It is demonstrated that the flow predictions are of equivalent quality on both structured and unstructured grids. The influence of the geometrical details (e.g. nacelle and tower) on the wake development as well as the influence of the discretization scheme are also investigated.