Prediction of the unsteady aerodynamic characteristics of horizontal axis wind turbines including three-dimensional effects

Abstract

An unsteady aerodynamic model for horizontal axis wind turbine performance prediction has been extended to consider three-dimensional (3D) rotational effects. The method couples a prescribed wake vortex scheme with a semi-empirical unsteady aerofoil model to provide the unsteady response of the blades due to the cyclic variation of incidence. The wake geometry of the turbine and the basic aerodynamic parameters required by the unsteady aerofoil model are calculated from the prescribed wake model using two-dimensional aerofoil data. The 3D rotational effects are then taken into account by a series of corrections to the unsteady aerofoil model. Application of these corrections has yielded substantial improvements in the prediction of aerodynamic force and moment coefficients on inboard blade sections. This is illustrated by a series of comparisons with field data. In general, the method is shown to give accurate predictions over a range of operating conditions and inflow angles.

Large-scale wind turbine blade design and aerodynamic analysis

“…A prescribed wake approach [24], which is coupled with a dynamic stall model and a threedimensional rotational effect model, has been used in the Blind Comparison organized by the National Renewable Energy Laboratories [25]. Although computationally efficient, prescribed wake methods are strictly limited in many complex conditions due to lack of sufficient and reliable data for the wake description.…”

An examination of key aerodynamic modelling issues raised by the NREL blind comparison

“…The HAWTDAWG model was initially developed as a prediction tool for the aerodynamics of horizontal axis wind turbines in steady head-on flow. 13 Subsequently, however, its capability was extended to include prediction of the unsteady aerodynamics of the blades in yawed inflow 14 and in the tower shadow on downwind machines. 15,16 The main features of the method have been detailed elsewhere 9,13,14 but, for completeness, are outlined below.…”

“…13 Subsequently, however, its capability was extended to include prediction of the unsteady aerodynamics of the blades in yawed inflow 14 and in the tower shadow on downwind machines. 15,16 The main features of the method have been detailed elsewhere 9,13,14 but, for completeness, are outlined below. In the model the blade is represented as a series of blade elements, from which trail vortex filaments whose strengths correspond to the differences in bound circulation between adjacent blade elements.…”

“…Unsteady loads acting on the rotor blades, due to yawed inflow and tower shadow effects, are evaluated using the Beddoes-Leishman unsteady performance model. 17 This semi-empirical model is very efficient owing to its explicit algebraic format and has been successfully used in the prediction of air loads for both HAWTs 5,9,14 and VAWTs. 18,19 In this model, unsteady effects in attached flow conditions are simulated by the superposition of indicial aerodynamic responses for time step changes in angle of attack, including In modelling the performance of an aerofoil in unsteady flow, the technique described above implicitly includes the induced effect of the shed vorticity downstream of the aerofoil.…”

Dimensional Deviation Estimation for Parts with Free-Form Surfaces

“…Unlike regular geometric features, free-form surfaces can provide excellent mechanical properties, optical characteristics, fluid characteristics, and so on. Geometric shapes of parts with free-form surfaces are often closely related to parts' design performance [1,2]. Meanwhile, dimensional accuracy will have a direct impact on parts' quality and performance [3].…”