Investigation of the validity of BEM for simulation of wind turbines in complex load cases and comparison with experiment and CFD

H Rahimi,J Peinke,B Dose,B Stoevesandt

doi:10.1088/1742-6596/749/1/012015

Abstract

The aim of this work is to investigate the validity of simulation codes based on the Blade Element Momentum (BEM) theory for three important design load conditions. This paper includes the cases of yawed inflow, rotor tower interaction for downwind turbines and the standstill case. Computational Fluid Dynamics (CFD) and experimental data (when available) are used for the evaluation of the obtained results. For the yawed inflow, the results indicate that significant deviations between BEM and experiments & CFD can be observed. This discrepancy is caused by unsteady phenomena such as the advancing & retreating blade effect and the skewed wake effect. In the case of the rotor and tower interaction of the downwind turbine, the results show that the BEM based code overpredicts the sectional forces in terms of the normal and tangential forces by 20%. In the case of standstill, the evaluation of the results based on tip deflections shows clear differences in the output of both numerical approaches. While the flapwise deflections show a reasonable agreement, the CFD-based coupled solver predicts much larger edgewise vibrations.

Highlights

One of the most common approaches to simulate the aerodynamics of wind turbines is the Blade Element Momentum (BEM) theory
Low cost in simulations, which is a result of this two dimensional theory, makes the simulation of more than thousand load cases within a short amount of time affordable
Complex three dimensional flows which occur in the wind turbines cannot be captured by the BEM model

Summary

Introduction

1. Introduction One of the most common approaches to simulate the aerodynamics of wind turbines is the Blade Element Momentum (BEM) theory. Complex three dimensional flows which occur in the wind turbines cannot be captured by the BEM model. Several experimental and numerical studies showed that codes based on BEM are often not sufficiently accurate and reliable for predicting complex aerodynamic behavior acting on the wind turbine blades [1, 2].

Results

Conclusion