A Practical Approach in the CFD Simulation of Off-shore Wind Farms through the Actuator Disc Technique (original) (raw)
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An application of the actuator disc model for wind turbine wakes calculations
Applied Energy, 2013
h i g h l i g h t s " In this study a novel technique for wind turbine wakes simulation was implemented. " Production data from a small coastal wind farm in Finland were used for validation. " Results demonstrate an improvement comparing to the traditional analytical models. " Such model can be usefully implemented for large offshore wind farm wakes simulation.
Comparison of CFD Prediction and Actual Condition for Wake Effect on an Onshore Wind Farm
International Journal of Renewable Energy Research, 2018
In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terrain, Computational Fluid Dynamics (CFD) simulations were performed with the WindModeller software, which is a module for wind farm simulation developed by ANSYS. The wake is modelled using an actuator disc model approach which is based on the wind turbine thrust coefficient and wind speed. A WindModeller simulation was carried out for DBK wind farm located on Jeju Island, Korea. The nacelle wind speed data from 15 Hanjin 2MW turbines were collected through the Supervisory Control And Data Acquisition (SCADA) system. The wind data was measured from a 80m tall met mast near the wind farm, which was used as a reference. The WindModeller module simulated the wind speed and turbulence intensity within the terrain with a wind speed of 9.3 m/s and a wind direction of 314 degrees. The wakes from single and multiple turbines were predicted by the WindModeller simulation were compared with the ac...
Wakes Calculation in a Offshore Wind Farm
Wind Engineering, 2013
This paper is focusing on the wake modeling in large offshore wind farms. Over the sea the ambient turbulence is much lower than onshore, wakes persist for long distances, mixing in a complex pattern. Hence an accurate evaluation of the wakes become crucial in the estimation both of the production and loads. Regarding loads the main effect of the turbines wakes is an increase of turbulence compared to the ambient one. A careful assessment of the wakes is therefore required when analyzing offshore wind farms. The approaches in estimating the wake losses go from simple theoretical or empirical laws to full rotor aerodynamic calculations; in between there is a range of intermediate calculations. Two approaches will be presented: the use of relative simple equations (also called analytical models) which are the standards in the wind resource assessment and a more accurate, but computationally more demanding, the actuator disc technique.
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.
We present here a computational fluid dynamics (CFD) simulation of Lillgrund offshore wind farm, which is located in the Øresund Strait between Sweden and Denmark. The simulation combines a dynamic representation of wind turbines embedded within a large-eddy simulation CFD solver and uses hr-adaptive meshing to increase or decrease mesh resolution where required. This allows the resolution of both large-scale flow structures around the wind farm, and the local flow conditions at individual turbines; consequently, the response of each turbine to local conditions can be modelled, as well as the resulting evolution of the turbine wakes. This paper provides a detailed description of the turbine model which simulates the interaction between the wind, the turbine rotors, and the turbine generators by calculating the forces on the rotor, the body forces on the air, and instantaneous power output. This model was used to investigate a selection of key wind speeds and directions, investigating cases where a row of turbines would be fully aligned with the wind or at specific angles to the wind. Results shown here include presentations of the spin-up of turbines, the observation of eddies moving through the turbine array, meandering turbine wakes, and an extensive wind farm wake several kilometres in length. The key measurement available for cross-validation with operational wind farm data is the power output from the individual turbines, where the effect of unsteady turbine wakes on the performance of downstream turbines was a main point of interest. The results from the simulations were compared to the performance measurements from the real wind farm to provide a firm quantitative validation of this methodology. Having achieved good agree- ment between the model results and actual wind farm measurements, the potential of the methodology to provide a tool for further investigations of engineering and atmospheric science problems is outlined.
Full rotor modelling and generalized actuator disc for wind turbine wake investigation
Energy Reports, 2020
This paper purpose a numerical study of the flow downstream a wind turbine erected in the neutral atmospheric boundary layer. A first part consists of unsteady wind flow simulations through a full moving rotor, which lets identifying the vortex generated in the wind turbine wake. The governed equations were solved in two sub-domains (Rotor/Stator) and the moved fluid flow continuity at the domain interface was managed by the Sliding Mesh technique of Turbo-machinery implemented in an open-source 'Code _Saturne'. However, the unsteady full rotor calculations proved to be extensive and inadequate for optimizing the wind farm layout. Therefore, to achieve a more accessible wake model, the second part consists of the design of a generalized hybrid wake model in which, contrary to the full simulation, an actuator disc 'with non-zero thicknesses' has substituted the rotor and was coupled to the Reynolds averaged Navier Stokes equations (RANS) through additional source terms. The modified k-ε was used to model the turbulence developed downstream the rotor. The ability of the proposed model to represent the wake was demonstrated by a series of validations with experimental data and results were in good agreement. c
Modelling wind turbine wakes for wind farms
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.
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.
Journal of Physics: Conference Series, 2019
The present work evaluates the benefits obtained when different levels of geometric and aerodynamic information of wind turbine blades are included in the actuator disc (AD) model, progressively increasing its descriptive capabilities. A novel AD model is presented, equivalent in precision to the AD coupled with the blade element momentum method, but avoiding the need to modify the CFD code by the use of a pre-calculated table. It is compared against three classical AD models, particularly aiming at the simulation of the wind farm wake interaction. The NREL-5MW reference wind turbine is adopted as test case, and configurations with single and two shifted wind turbines are analyzed.