Investigation of the NREL phase VI experiment with the incompressible CFD solver THETA

Länger-Möller, Annika; Löwe, Johannes; Kessler, Roland

doi:10.1002/we.2107

Cited by 17 publications

(23 citation statements)

References 20 publications

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“…The involved governing equations are the incompressible RANS equations. A comparison between an incompressible solver and a compressible solver was made by Länger-Möller [28] for the NREL Phase VI rotor. The results of the two solvers were almost identical.…”

Section: Simulation Methodsmentioning

confidence: 99%

Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration

et al. 2018

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Stall, a complex phenomenon related to flow separation, is difficult to be predicted accurately. The motivation of the present study is to propose an approach to improve the simulation accuracy of Reynolds Averaged Navier-Stokes equations (RANS) for wind turbines in stall. The approach is implemented in three steps in simulations of the S809 airfoil and the NREL (National Renewable Energy Laboratory) Phase VI rotor. The similarity between airfoil and rotor simulations is firstly investigated. It is found that the primary reason for the inaccuracy of rotor simulation is not the rotational effect or the 3-D effect, but the turbulence-related problem that already exists in airfoil simulation. Secondly, a coefficient of the SST turbulence model is calibrated in airfoil simulation, ensuring the onset and development of the light stall are predicted accurately. The lift of the airfoil in the light stall, which was overestimated about 30%, is reduced to a level consistent with experimental data. Thirdly, the calibrated coefficient is applied to rotor simulation. That makes the flow patterns on the blade properly simulated and the pressure distribution of the blade, as well as the torque of the rotor, are predicted more accurately. The relative error of the predicted maximum torque is reduced from 34.4% to 3.2%. Furthermore, the procedure of calibration is applied to the MEXICO (Model Experiments in Controlled Conditions) rotor, and the predicted pressure distributions over blade sections are better than the CFD (Computational Fluid Dynamics) results from the Mexnext project. In essence, the present study provides an approach for calibrating rotor simulation using airfoil experimental data, which enhances the potential of RANS in accurate simulation of the wind turbine aerodynamic performance.

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Section: Simulation Methodsmentioning

confidence: 99%

Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration

et al. 2018

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“…Is it the ABL values that are comparatively high or the wind tunnel values that allow for solving at a very low turbulence intensity? Both issues are addressed by a systematic study with the incompressible U‐RANS solver THETA . A generic model of the ENERCON E44 HAWT is chosen to represent an industrial wind turbine that operates at a tip speed ratio (TSR) λ = 6.…”

Section: Introductionmentioning

confidence: 99%

Impact of wall roughness and turbulence level on the performance of a horizontal axis wind turbine with the U‐RANS solver THETA

Länger-Möller¹

2019

Wind Energy

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The presented work investigates the impact of different sheared velocity profiles in the atmospheric boundary layer on the characteristics of a wind turbine by modifying the wall roughness coefficients in the logarithmic velocity profile. Moreover, the rotor and wake characteristics in dependence of the turbulence boundary conditions are investigated. In variant I, the turbulence boundary conditions are defined in accordance to the logarithmic velocity profile with different wall roughness lengths. In variant II, the turbulent kinetic energy and turbulent viscosity remain independent of the velocity profile and represent the free‐stream turbulence level. With an increase of the shear in the velocity profile, the amplitudes in the 3/rev characteristics of rotor thrust and rotor torque, induction factors, and effective angles of attack are increased. In variant I, the overall levels of thrust coefficient are hardly affected by the velocity profiles resulting from different wall roughness length values. The power coefficient is reduced about 1%. Conversely, compared with variant II, a difference of 2% in the power coefficient has been detected. Moreover, the wake recovery process strongly depends on the turbulence boundary condition. Simulations are carried out on an industrial 900‐kW wind turbine with the incompressible U‐RANS solver THETA.

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“…The validation of the resolved-gust approach in the DLR URANS solver THETA (Löwe et al, 2015;Länger-Möller, 2017) is presented herein. To reduce the complexity of the problem and emphasize the quality of the resolved-gust approach, the NREL 5 MW wind turbine is chosen to operate in shear-free conditions.…”

Section: Introductionmentioning

confidence: 99%

Simulation of transient gusts on the NREL 5 MW wind turbine using the URANS solver THETA

Länger-Möller¹

2018

Wind Energ. Sci.

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Abstract.A procedure to propagate longitudinal transient gusts through a flow field by using the resolved-gust approach is implemented in the URANS solver THETA. Both the gust strike of a 1 − cos() gust and an extreme operating gust following the IEC 61400-1 standard are investigated on the generic NREL 5 MW wind turbine at rated operating conditions. The impact of both gusts on pressure distributions, rotor thrust, rotor torque, and flow states on the blade are examined and quantified. The flow states on the rotor blade before the gust strike at maximum and minimum gust velocity are compared. An increased blade loading is detectable in the pressure coefficients and integrated blade loads. The friction force coefficients indicate the dynamic separation and reattachment of the flow during the gust. Moreover, a verification of the method is performed by comparing the rotor torque during the extreme operating gust to results of FAST rotor code.

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Investigation of the NREL phase VI experiment with the incompressible CFD solver THETA

Cited by 17 publications

References 20 publications

Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration

Accurate RANS Simulation of Wind Turbine Stall by Turbulence Coefficient Calibration

Impact of wall roughness and turbulence level on the performance of a horizontal axis wind turbine with the U‐RANS solver THETA

Simulation of transient gusts on the NREL 5 MW wind turbine using the URANS solver THETA

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