Comparison of wind turbine loads inside a wake between engineering model and CFD calculation

B Roscher,Y Shkara,G Jacobs,L Stössel,A Werkmeister,R Schelenz

doi:10.1088/1742-6596/1037/7/072039

Abstract

Depending on location and inflow situations, a wind turbine experiences a variety of loads. Especially when considering that wind turbines are placed in a cluster. Inside wind farms, the wind turbines experience wake effects. This effect results in an increased turbulence intensity and therefore into higher loads onto the wind turbine components. Such increased load situation could lead to an early fatigue failure. For this reason, it is necessary to investigate the influence of wake effect on the wind turbine loading. Multiple wake models have been developed to represent and inspect the wake effects. This paper will utilize the method proposed by the IEC 61400 norm versus an inflow field generated by a Computational Fluid Model. The resulting 3D wind fields are used as an input into a multi-body simulation environment. This is done to determine the influence on the receiving wind turbine. The comparison will be inspected at the rotor hub coordinate system, as suggested by the Germanischen Lloyd, such that influencing parameter can be minimized. It was determined that in case of a partial wake inflow the results of the CFD indicate a higher load variation in bending and tilt direction.

Highlights

Since 2017, it is mandatory to announce new wind farms via an auction system in Germany
Comparison of IEC and CFD flow field These first results show that the wake effect needs to be considered in wind parks for different partial wake effects
The results indicated that for special inflow situation, i.e. partial wake, the proposed methods are not sophisticated enough to be used to determine bending moments

Summary

Introduction

Since 2017, it is mandatory to announce new wind farms via an auction system in Germany. Onshore the distance between wind turbines varies between 3 and 5 rotor diameters. Such a close spacing has certain disadvantages. While the wind turbine extracts energy out of the wind, the flow afterwards will be changed. The characteristics of such a downstream flow, called wake effect, can be differentiated into two aspects. The mean wind speed is reduced and secondly, the flow field will have an increased turbulence. These turbulences put wind turbine under a lot of stress, which is experiencing such a flow. To avoid any critical damage or early fatigue, the influence of wind turbines need to be known and evaluated

Results

Discussion

Conclusion