Coupling of an Unsteady Lifting Line Free Vortex Wake Code to the Aeroelastic HAWT Simulation Suite FAST

Abstract

A coupling of the Lifting Line Free Vortex Wake (LLFVW) model of the open source wind turbine software QBlade and the wind turbine structural analysis tool FAST has been achieved. FAST has been modified and compiled as a dynamic library, taking rotor blade loading from the LLFVW model as input. Most current wind turbine aeroelastic simulations make use of the Blade Element Momentum (BEM) model, based upon a number of simplifying assumptions which are often violated in unsteady situations. The purpose of the implemented model is to improve accuracy under unsteady conditions. The coupling has been thoroughly validated against the NREL 5MW reference turbine. The turbine is compared under both steady conditions and three unsteady operating conditions to the BEM code AeroDyn. The turbine has been simulated operating at a constant RPM and with a variable-speed, variable blade-pitch-to-feather controller. Under steady conditions the agreement between the LLFVW and AeroDyn is demonstrated to be very good. The LLFVW produces different predictions for rotor power, blade deflection and blade loading during transient conditions. A number of important observations have been made which illustrate the necessity of a higher fidelity aerodynamic model. The validation and results are considered as a step towards the implementation of an open-source, high fidelity aeroelastic tool for wind turbines.

Response to Reviewers

“…The QBlade LLFVW implementation has been previously tested for a range of standard HAWT and VAWT cases as can be found in the existing literature (Marten et al, 2015;Saverin et al, 2016). When the wind turbine starts moving relative to the steady inflow, the wake will become distorted.…”

“…Recently, the implementation of an LLFVW code was completed and included in the QBlade wind turbine simulation code (Marten et al, 2015). Simultaneously to this study, the LLFVW solver was extended to include an unsteady aerodynamics model 2 and coupled with the structural formulations of the FAST framework (Wendler et al, 2016;Saverin et al, 2016). In this paper, a comparison is made between the LLFVW code and existing literature comparisons in which higher-order aerodynamic simulation techniques were used, i.e.…”

Three-dimensional CFD Analysis of Performance of Small-scale Hawt based on Modified NACA-4415 Airfoil

“…CFD simulation can be used to analysis the Lifting Line Theory (LLT) and the Non Lifting Line Free Vortex Wake Algorithm (LLFVW) as previously reported by Garrel (2003). The LLT have been used to calculate a vortex core model on HAWT as done by Marten et al (2015), Marten et al (2016) and Saverin et al (2016) and by Wendler et al (2016) for VAWT.…”

Modern methods for investigating the stability of a pitching floating platform wind turbine

“…The QBlade LLFVW implementation has been previously tested for a range of standard HAWT and VAWT cases as can be found in the existing literature Saverin et al, 2016). When the wind turbine starts moving relative to the steady inflow, the wake will become distorted.…”

“…Recently, the implementation of an LLFVW code was completed and included in the QBlade wind turbine simulation code . Simultaneously to this study, the LLFVW solver was extended to include an unsteady aerodynamics model 2 and coupled with the structural formulations of the FAST framework (Wendler et al, 2016;Saverin et al, 2016). In this paper, a comparison is made between the LLFVW code and existing literature comparisons in which higher-order aerodynamic simulation techniques were used, i.e.…”