Investigating the Level of Fidelity of an Actuator Line Model in Predicting Loads and Deflections of Rotating Blades under Uniform Free-Stream Flow

Abstract

In this paper, the accuracy of an in-house Actuator Line (AL) model is tested on aeroelastic simulations of a Wind Turbine (WT) rotor and a helicopter Main Rotor (MR) under uniform free-stream flow. For the scope of aeroelastic analyses, the AL model is coupled with an in-house multibody dynamics code in which the blades are modeled as beams. The advantage from the introduction of CFD analysis in rotorcraft aeroelasticity is related to its capability to account in detail for the interaction of the rotor wake with the boundary layer developed on the surrounding bodies. This has proven to be of great importance in order to accurately estimate the aerodynamic forces and thus the corresponding structural loads and deflections of the blades. In wind turbine applications, a good example of the above is the rotor/ground interaction. In helicopter configurations, the interaction of MR with the ground or the fuselage and the interaction of tail rotor with the duct in fenestron configurations are typical examples. Furthermore, CFD aerodynamic analysis is an obvious modeling option in which the above mentioned asset can be combined with the consideration of the mutual interaction of the rotor with the ambient turbulence. A WT rotor operating inside the atmospheric boundary layer under turbulent free-stream flow is such a case. In the paper, AL results are compared against Blade Element Momentum (BEM) and Lifting Line (LL) model results in the case of the WT, whereas LL and measured data are considered in the helicopter cases. Blade loads and deflections are mainly compared as azimuthal variations. In the helicopter MR cases, where comparison is made against experimental data, harmonic analysis of structural loads is shown as well. Overall, AL proves to be as reliable as LL in the canonical cases addressed in this paper in terms of loads and deflections predictions. Therefore, it can be trusted in more complex flow conditions where viscous effects are pronounced.

Comparative Study of the Blade Number and Airfoil Profile Impacts on the Twist/Chord Distribution of a Small Wind Turbine Blade

“…The BEM model, which is the basic and classical method for analyzing the performance of wind turbines [33], was utilized to compute the C p as well as the Q s . In this approach, the blade is divided into several independent strips, which aerodynamically behave like two-dimensional airfoils, and the aerodynamic forces are calculated based on local flow conditions [34]. The BEM is a combination of the blade element and momentum theories.…”

Evaluation of Regional Elevation and Blade Density Effects on the Efficiency of a 1-kW Wind Turbine for Operation in Low-Wind Counties in Iran

“…To do so, the blade was segmented into multiple distinct regions (elements), which exhibit aerodynamics behaviors similar to two-dimensional airfoils. Then, the aerodynamic forces were computed according to the local flow circumstances [66].…”

A flexible actuator curve model for aeroelastic simulations of wind turbines in atmospheric boundary layers

“…Sessarego et al [11] coupled the HAWC2 structural solver to a three-dimensional viscous-inviscid interactive solver. Meng et al or Spyropoulos et al [12,13] used a deformable actuator line in a URANS code to compare their result to a FAST or a BEM method. To the authors knowledge, a deformable actuator line method enabled in a LES code with a turbulent inflow has not yet been studied in depth.…”