Chaired by: F. Porté-Agel, J. Jonkman
13:30
Determination of Scaled Wind Turbine Rotor Characteristics from 3 Dimensional RANS Calculations
Simon Burmester | MARIN (Maritime Research Institute Netherlands) | Netherlands
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Authors:
Simon Burmester | MARIN (Maritime Research Institute Netherlands) | Netherlands
Sebastien Gueydon | Netherlands
Michel Make | Netherlands
Previous studies have shown the importance of 3D effects when calculating the performance characteristics of a scaled down turbine rotor. In this paper the results of 3D RANS computations are taken to calculate 2D lift and drag coefficients. These coefficients are assigned to FAST as input parameters. Then, the rotor characteristics (CT and CP) are calculated using BEMT. This coupling of RANS and BEMT was previously applied by other parties and is termed here the RANS-BEMT coupled approach. The approach is compared to measurements carried out in a wave basin at MARIN applying Froude scaled wind, and the direct 3D RANS computation. The data of both a model and full scale wind turbine are used for V&V. The flow around a turbine blade at full scale has a more 2D character than the flow around a turbine blade at model scale. Since BEMT assumes 2D flow behaviour, the results of the RANS-BEMT coupled approach agree better with the results of the CFD simulation at full- than at model-scale.
13:50
Accurate load prediction by BEM with airfoil data from 3D RANS simulations
Marc Sebastian Schneider | German Aerospace Center | Germany
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Authors:
Marc Sebastian Schneider | German Aerospace Center | Germany
Jens Nitzsche | Germany
Holger Hennings | Germany
Two methods for the extraction of airfoil coefficients from 3D CFD simulations of a wind turbine rotor are investigated, and these coefficients are used to improve the load prediction of a BEM code. The coefficients are extracted from a number of steady RANS simulations using different methods for calculation of the induction factor in the rotor plane. It is shown that these 3D rotor polars are able to capture the rotational augmentation at the inner part of the blade as well as the load reduction by 3D effects close to the blade tip. They are used as input to a simple BEM code and the results of this BEM with 3D rotor polars are compared to the predictions of BEM with 2D airfoil coefficients plus common empirical corrections. While BEM with 2D airfoil coefficients produces a very different radial distribution of loads than the RANS simulation, the BEM with 3D rotor polars manages to reproduce the loads from RANS very accurately for a variety of load cases.
14:10
A stochastic aerodynamic model for stationary blades in unsteady 3D wind fields
Manuel Fluck | University of Victoria | Canada
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Authors:
Manuel Fluck | University of Victoria | Canada
Curran Crawford | Canada
Dynamic loads play an important roll in wind turbine design, but establishing life-time aerodynamic loads (e.g. extreme and fatigue loads) is computationally expensive. Conventional (deterministic) methods to analyze long term loads rely on the repeated analysis of multiple wind samples and are usually too expensive to be included in optimization routines. We present a new stochastic approach, which solves the aerodynamic system equations in a stochastic space, thus arriving directly at a stochastic description of the coupled blade loads. This new approach removes the requirement of analyzing multiple realizations. Instead, long term loads are extracted from a single stochastic solution, a procedure that is obviously significantly faster. Despite the reduced analysis time, results obtained from the stochastic approach match deterministic result well for a simple test-case (stationary blade). Thus, this method opens up new avenues to include long term loads into turbine optimization.
14:30
Development of an engineering code for the implementation of aerodynamic control devices in BEM
Maria Aparicio | CENER | Spain
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Authors:
Maria Aparicio | CENER | Spain
Ãlvaro González | Spain
Sugoi Gomez-Iradi | Spain
Xabier Munduate | Spain
Aeroelastic codes based on Blade Element Momentum theory are the standard used by many wind turbine designers. These codes usually include models and corrections for unsteady aerodynamics, tip and root effect, tower shadow and other effects. In general, this kind of codes does not include models to correctly simulate aerodynamic control devices. This paper presents some modifications including the unsteady contributions due to the flap motion (based on indicial models) and the spanwise (3D) effects (based on circulation theory), in order to simulate flaps in the blades using engineering codes. This method can be included in BEM codes in general and it could be also applied to another kind of control devices. The validation and verification show the accuracy of this method using experimental data for two-dimensional unsteady cases, and CFD for three-dimensional steady and unsteady cases.
14:50
Investigation of the current yaw engineering models for simulation of wind turbines in BEM and comparison with CFD and experiment
Hamid Rahimi | ForWind - University of Oldenburg | Germany
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Authors:
Hamid Rahimi | ForWind - University of Oldenburg | Germany
Bastian Dose | Germany
Joachim Peinke | Germany
Gerard Schepers | Germany
The aim of this work is to investigate the capabilities of current engineering tools based on Blade Element Momentum (BEM) and free vortex wake codes for the prediction of key aerodynamic parameters of wind turbines in yawed flow. Axial induction factor and aerodynamic loads of three wind turbines (NREL VI, AVATAR and INNWIND.EU) were investigated using wind tunnel measurements and numerical simulations for 0 and 30 degrees of yaw. Results indicated that for axial conditions there is a good agreement between all codes in terms of mean values of aerodynamic parameters, however in yawed flow significant deviations were observed. This was due to unsteady phenomena such as advancing & retreating and skewed wake effect. These deviations were more visible in aerodynamic parameters in comparison to the rotor azimuthal angle for the sections at the root and tip where the skewed wake effect plays a major role.
15:10
Wind speed and direction prediction by WRF and WindSim coupling
Muhammad Bilal | The Arctic University of Norway | Norway
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Authors:
Kine Solbakken | The Arctic University of Norway, UiT | Norway
Kine Solbakken | Norway
Yngve Birkelund | Norway
Muhammad Bilal | The Arctic University of Norway | Norway
In this study, the performance of the mesoscale meteorological Weather Research and Forecast (WRF) model coupled with the microscale computational fluid dynamics based model WindSim is investigated and compared to the performance of WRF alone. The two model set-ups, WRF and WRF-WindSim, have been tested on three high-wind events in February, June and October, over a complex terrain at Nygårdsfjell wind park in Norway. The wind speeds and wind directions are compared to measurements and the results are evaluated based on root mean square error, bias and standard deviation error. Both model set-ups are able to reproduce the high wind events. For the winter month February the WRF-WindSim performed better than WRF alone, with the RMSE decreasing from 2.86 to 2.38 and STDE decreasing from 2.69 to 2.37. For the two other months no such improvements were found. The best model performance was found in October where the WRF had a RMSE of 1.76 and STDE 1.68. For June, both model set-ups under estimate the wind speed. Overall, the adopted coupling method of using WRF outputs as virtual climatology for coupling WRF and WindSim did not offer a significant improvement over the complex terrain of Nygårdsfjell. However, proposed coupling method offers high degree of simplicity when it comes to its application. Further testing is recommended over larger number of test cases to make a significant conclusion.