Evaluation and Control of Loads on Wind Turbines under Different Operating Conditions by Means of CFD

This article presents results from Computational Fluid Dynamics (CFD) simulations of wind turbines performed within the project WEALoads. The project is devoted to the unsteady load response of wind turbines under realistic environmental conditions and to mechanisms to control these loads. An extract of the latest research done on these topics is presented in this article. Based on previous studies of wind turbines in complex terrain done by the authors the effects of the terrain on the load response is tried to break down to several single events. Some of these are the shear of the wind profile, turbulence intensity of the inflow, inclined inflow or yawed inflow. In this article the effect of yawed inflow on the loads and aerodynamics of a wind turbine is described in further detail. The second part of the studies is dedicated to the control of wind turbine loads which is one of the key factors in the current turbine design processes. An example to reduce load fluctuations caused by tower blockage is shown. This can be seen as a prove of concept for the method applied. All of the simulations were performed using the flow solver FLOWer from DLR (German Aerospace Center). For the studies of the first part a Detached Eddy Simulations (DES) approach was used whereas for the second part URANS methods were applied. Afterwards, a newly implemented DES method giving a more realistic prediction of the flow field around the turbine and consequently the loads is described in more detail. The general outcome of the article is that a load reduction under yawed inflow can be observed as well as a wake deflection which is of high importance in case of wind park development and control. Moreover, a bridge between the yaw results, the load reduction method and the new high fidelity DES methods is build to give an outlook to future works.