Validating BEM, Direct and Inverse Free Wake Models with the MEXICO Experiment.

Abstract

The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data for validation of models for wind turbines. Kulite c pressure sensors were used for pressure measurements while Particle Image Velocimetry was used with the aim of tracking the tip vortex trajectory. The pressure measurements were carried out for both axial and yawed flow conditions with yaw angles of 15 o , 30 o and 45 o . For the Particle Image Velocimetry measurements data was gathered for axial flow and for the ±30 o yaw cases at a single tip speed ratio. In this work, an inverse free wake lifting line model, a direct free wake model and a BEM model are validated with the MEXICO data. Particular emphasis is placed on the study of yawed flow conditions. The inverse free-wake model makes use of the experimental loads as input in order to find the distribution of inductions and angle of attack. The predictive capability of BEM may therefore be assessed based on this. Validation of the inverse free-wake model was performed by investigating the stagnation pressure prediction as well as the vortex trajectory prediction. This was done by means of the PIV data gathered from the MEXICO experiment. This PIV data was also used for validation purposes of the direct free-wake model. The differences in the angle of attack distributions in yawed flow with these models was studied in order to assess the difference in results between the use of 2D and 3D airfoil data.

Characterization of the unsteady aerodynamics of offshore floating wind turbines

“…The next generation of wind turbine aerodynamic analysis tools—computational fluid dynamics and free vortex models— may improve the simulation of complex aerodynamic operating conditions. However, these techniques are predominantly used as research tools.…”

Validation of the Beddoes–Leishman dynamic stall model for horizontal axis wind turbines using MEXICO data

“…BEM theory can be considered simple, and it has been derived several decades ago; but still, it is used in present days, mostly but not only in preliminary stages of HAWT design. Other more complex approaches include actuator line theory and vortex wake theory, both computationally very consuming. Actuator line theory solves full 3D Reynolds Averaged Navier–Stokes equations around the HAWT rotor and introduces the rotating blade forces contribution through source terms along lines representing the blades.…”

A Solution-Based Stall Delay Model for Horizontal-Axis Wind Turbines

“…In the NREL Phase VI rotor experiment, 43,52 sectional angles of attack were measured at five spanwise stations by means of five-hole probes mounted ahead of the blade leading edge. These served as data for a later development of an inverse free-wake lifting line model 53,54 that produced both accurate and consistent angle-of-attack data for both the NREL Phase VI and MEXICO experiments, see also Schreck et al 47 Computed angles of attack shown in Figure 10 were extracted directly from the computations over the range of wind speeds shown in Figure 9. At the 30% radial station in Figure 10(a), a large amount of correction to the normal force coefficient is apparent for the SBSD when compared with the 2D polar data.…”