Nonlinear inviscid aerodynamics of a wind turbine rotor in surge, sway, and yaw motions using a free-wake panel method

Abstract

Abstract. We investigate the aerodynamics of a surging, heaving, and yawing wind turbine with numerical simulations based on a free-wake panel method. We focus on the UNAFLOW (UNsteady Aerodynamics of FLOating Wind turbines) case: a surging wind turbine which was modeled experimentally and with various numerical methods. Good agreement with experimental data is observed for amplitude and phase of the thrust with surge motion. We achieve numerical results of a wind turbine wake that accurately reproduce experimentally verified effects of surging motion. We then extend our simulations beyond the frequency range of the UNAFLOW experiments and reach results that do not follow a quasi-steady response for surge. Finally, simulations are done with the turbine in yaw and heave motion, and the impact of the wake motion on the blade thrust is examined. Our work seeks to contribute a different method to the pool of results for the UNAFLOW case while extending the analysis to conditions that have not been simulated before and providing insights into nonlinear aerodynamic effects of wind turbine motion.

Wind turbine rotors in surge motion: New insights into unsteady aerodynamics of FOWT from experiments and simulations

“…b vel > 15%) of the surging NREL 5 MW rotor around the design operation condition, Wen et al found that the rise of the power amplitude becomes slightly nonlinear. A similar observation was found by Ribeiro et al (2023) for the thrust force, where a FVW panel method was used to simulate the UNAFLOW rotor. In addition, a rising phase shift between the surge velocity and rotor thrust was reported independent from b vel , which was also observed by Mancini et al (2020) earlier.…”

“…A hint on such behaviour can also be found in Ribeiro et al (2023). Panel method simulations showed a lower-than-expected thrust amplitude at a rotor reduced frequency slightly below 5.…”

“…However, these assumptions are only valid for moderate b vel and the absolute limits are dependent on 200 the special case. In the FVW and RANS simulations of Mancini et al (2020) and Ribeiro et al (2023), a linear rise of the thrust amplitude ∆T , which is normalised by the motion amplitude A, with the motion frequency is present. This can be expressed as:…”

Resolvent-based motion-to-wake modelling of wind turbine wakes under dynamic rotor motion

“…When assuming an inflow without shear and an axisymmetric wake, yaw can be considered equivalent to pitch; sway can be considered equivalent to heave, following a coordinate transformation. At small amplitude, the roll motion of FOWT can be approximated by the sway motion since the centre of gravity is far below the rotor hub centre (Ribeiro, Casalino & Ferreira 2023a). Here, we assume that the FOWT is forced to oscillate harmonically for each motion.…”

Free Wake Panel Method Simulations of a Highly Flexible Wing in Flutter and Gusts

“…Simulations that do not include flow separation, but include geometric nonlinear effects have been shown to capture the amplitude of the LCO associated with the first flutter mode of the Pazy wing (Riso and Cesnik, 2022), but not the subcritical effects. In the case of the present simulations, nonlinear geometry effects come from the structural model, while nonlinear inviscid aerodynamic effects (Ribeiro et al, 2023), come from the panel code. Flow separation is missing, meaning capturing the subcritical LCO is likely not possible, but achieving LCO for the first flutter mode should be.…”