Experimentally validated three‐dimensional computational aerodynamics of wind turbine blade sections featuring leading edge erosion cavities

Abstract

Wind turbine blade leading edge erosion reduces the lift and increases the drag of the blade airfoils. This occurrence, in turn, reduces turbine power and energy yield. This study focuses on the aerodynamic analysis of large and sparse erosion cavities, observed in intermediate to advanced erosion stages, whose size and surface pattern do not lend themselves to experimental and numerical analysis by means of distributed roughness models alone. Making use of three‐dimensional Navier‐Stokes computational fluid dynamics enhanced by laminar‐to‐turbulent transition modeling, and geometrically resolving individual erosion cavities, the study validates this simulation‐based approach for predicting the aerodynamics and performance loss of blade sections featuring the aforementioned erosion cavities against available experimental data. It is found that the considered cavities can trigger transition, indicating the necessity of both resolving their geometry in the simulations and also modeling distributed surface roughness, of typically lower level, as this latter affects the properties of boundary layers and, if sufficiently high, may trigger transition over the entire spanwise length affected. The energy yield loss of a utility‐scale turbine due to the considered erosion pattern is found to be between 2.1% and 2.6% using measured and computed force data of the nominal and eroded outboard blade airfoil. A parametric analysis of the cavity geometry suggests that the geometry of the cavity edge has a much larger impact on aerodynamic performance than the cavity depth.

The significance of bypass transition on the annual energy production of an offshore wind turbine

“…These mean that without a quantitative understanding of the relationships between erosion characteristics and their impacts on AEP, direct comparisons with other studies may be harder to interpret. Similarly, it has been shown by Campobasso et al 34 The earlier studies included in Table 7 show predicted reductions in AEP due to blade erosion of several percent. However, in recent years, as service experience has grown, more information is becoming available on the levels of erosion damage that are being experienced by current generation turbines operating in the offshore environment.…”

“…These mean that without a quantitative understanding of the relationships between erosion characteristics and their impacts on AEP, direct comparisons with other studies may be harder to interpret. Similarly, it has been shown by Campobasso et al 34 that there are significantly different aerodynamic interactions when modelling roughness as individual elements or distributed over the surface, introducing further uncertainties. A purpose therefore of Table 7 is to highlight some of the characteristics modelled in recent studies to suggest where variations may result in the different predicted AEP losses.…”

Multi-scale Navier-Stokes analysis of geometrically resolved erosion of wind turbine blade leading edges

“…Wind turbine (WT) blade leading edge (LE) erosion can cause a significant reduction of the aerodynamic performance of the blade, and, thus, the turbine annual energy production (AEP). Several studies focused on estimating AEP losses due to WT blade LE erosion (LEE) [9,20,4], also developing experimentally validated methods for predicting AEP losses due to general LEE patterns [6,5,7].…”

Accuracy of the Gamma Re-Theta Transition Model for Simulating the DU-91-W2-250 Airfoil at High Reynolds Numbers

“…This is because the DU airfoil series are still young compared to, for example, the well-known NACA airfoil families [49][50][51] or with the popular the S809 airfoil [52]. So far, several works have been devoted to the validation of the aerodynamic performance of DU series profiles using advanced CFD tools [15,[53][54][55][56][57][58][59][60]. All of these articles, except papers [57,59,60], take into account CFD investigation of the DU 91-W2-250 airfoil.…”

“…So far, several works have been devoted to the validation of the aerodynamic performance of DU series profiles using advanced CFD tools [15,[53][54][55][56][57][58][59][60]. All of these articles, except papers [57,59,60], take into account CFD investigation of the DU 91-W2-250 airfoil.…”