Response Of Floating Wind Turbine Research Articles

SEAHOWL: Partitioned Multiphysics and Multifidelity Modelling of Wind Turbines with Monolithically Coupled Elastodynamics

We introduce SEAHOWL (Servo-Elasto-Aero-Hydro Offshore Wind Lab), a novel multiphysics multifidelity simulation framework for large-scale onshore, offshore, and floating wind turbines. For structural dynamics, multibody and finite element problems are coupled monolithically and solved within a single system of equations through Project Chrono, providing high numerical stability and optimal coupling accuracy. Combined with partitioned multiphysics, modularity is at the heart of the framework with various numerical methods and solvers (internal or external) available for each physics. This flexibility allows for the selection a target trade-off between numerical accuracy and computational efficiency on a use-case basis. Simulations showcased here have been selected through the prism of industrial R&D challenges, covering: controller response and loads over the operational wind range, 3P effect for different levels of fidelity for the blades, floating wind turbine response under irregular waves and turbulent wind, and innovative multibody application for 3P fatigue mitigation. SEAHOWL is cross-validated against the reference OpenFAST whole-turbine simulator from NREL, showing overall good agreement while differences between the two frameworks are highlighted.

Floating wind turbine response in uni- and multi-directional nonlinear waves by numerical and experimental investigations

Natural sea waves are typically multi-directional. However, the existing studies on the interaction of waves and structures mostly concentrate on uni-directional waves. In this study, using a higher-order boundary element method based on the nonlinear potential flow theory and the perturbation expansion technique, a numerical model is developed to investigate the hydrodynamic performance of a semi-submersible wind turbine foundation in uni- and multi-directional waves. Comprehensive validations with the wave-tank experiment are conducted. It is found that the significant platform response increases with the peak wave period in uni-directional irregular waves, while the high-frequency “energy” ratio changes little. The significant wave height hardly influences motion responses from either the time- or the frequency-domain perspective. In multi-directional irregular waves, the translational motions exhibit monotonicity with wave directionality. The energy concentration around the primary direction leads to a dominant wave-frequency motion and an increase in the high-frequency “energy” ratio. Although the individual modal motion responses are variable functions of wave nonlinearity, their averaged translational and rotational motions are nearly constant, indicating an energy transition or a trade-off relationship among the modal motions. In addition, unlike the uni-directional wave case, the low- and high-frequency “energy” ratios increase quadratically and decrease linearly with the significant wave height in multi-directional waves, respectively. All these findings demonstrate that wave directionality can change the wave–structure interaction properties and therefore needs to be adequately considered in engineering applications.

Similarity Model Development of Spar Floating Wind Turbine for Vibration Experimental Study

As the fixed foundation wind turbine no longer meets the design and cost requirements in deep sea power plant, and the offshore floating wind turbine (FOWT) suitable has been developed rapidly. The spar FOWT model is established in ANSYS-AQWA, and the influences of spectral peak frequency and incident angle for irregular waves on the vibration responses of FOWT are studied under five load cases. Under the guidance of similar theory, 1/150 scaled model has been simulated under typical load cases. The results show that the peak frequency of the spectrum has a significant effect on the vibration responses of FOWT, the incident angle also has a slight effect. By comparing the maximum and standard deviation (SD) of the tower top fore-aft displacement (TTDspFA) with the physical model and the experimental model, the minimum errors are 3.60% and 3.56%, respectively. This work will lay a foundation for experimental study on vibration of the floating wind turbine.

Development of performance specifications for hybrid modeling of floating wind turbines in wave basin tests

Hybrid modeling—combining physical testing and numerical simulation in real time—opens new opportunities in floating wind turbine research. Wave basin testing is an important validation step for floating support structure design, but the conventional approaches that use physical wind above the basin are limited by scaling problems in the aerodynamics. Applying wind turbine loads with an actuation system that is controlled by a simulation responding to the basin test in real time offers a way to avoid scaling problems and reduce cost barriers for floating wind turbine design validation in realistic coupled wind and wave conditions. This paper demonstrates the development of performance specifications for a system that couples a wave basin experiment with a wind turbine simulation. Two different points for the hybrid coupling are considered: the tower-base interface and the aero-rotor interface (the boundary between aerodynamics and the rotor structure). Analyzing simulations of three floating wind turbine designs across seven load cases reveals the motion and force requirements of the coupling system. By simulating errors in the hybrid coupling system, the sensitivity of the floating wind turbine response to coupling quality can be quantified. The sensitivity results can then be used to determine tolerances for motion tracking errors, force actuation errors, bandwidth limitations, and latency in the hybrid coupling system. These tolerances can guide the design of hybrid coupling systems to achieve desired levels of accuracy. An example demonstrates how the developed methods can be used to generate performance specifications for a system at 1:50 scale. Results show that sensitivities vary significantly between support structure designs and that coupling at the aero-rotor interface has less stringent requirements than those for coupling at the tower base. The methods and results presented here can inform design of future hybrid coupling systems and enhance understanding of how test results are affected by hybrid coupling quality.

Experimental observations of active blade pitch and generator control influence on floating wind turbine response

In this paper, the influence of wind turbine blade pitch and generator controls on the global response of a floating wind turbine is investigated. Several different active turbine controllers are considered and the resulting floating wind turbine global response is compared with that for a baseline configuration employing a fixed blade pitch and a fixed rotor speed. Results from platform pitch free-decay tests as well as a simultaneous dynamic wind and irregular sea state condition are used to understand the controllers' influence on floating wind turbine dynamic behavior.

Frequency domain approach for the coupled analysis of floating wind turbine system

ABSTRACTThis paper presents a simple frequency domain approach to predict the coupled response of floating wind turbine based on AQWA, and then investigates the effect of damping induced by wind, current and mooring system on the floating foundation response. This approach is validated against the experiment of DeepCwind floating offshore wind turbine in literatures. The results show reasonable agreement, and also indicate that the drift damping should be elaborated for the drift response. Based on this approach, the effect of wind and current on the floating wind turbine response is parametrically investigated. These aspects have rare effect on the wave frequency response, but affect the drift response due to the introduction of damping. The comparison between quasi-static and dynamic mooring line models reveals that the dynamics and added mass of mooring line play negligible roles, but the drag force significantly damps down the surge drift response.

Comparison of Spar and Semisubmersible Floater Concepts of Offshore Wind Turbines Using Long-Term Analysis

The long-term probability distributions of a spar-type and a semisubmersible-type offshore floating wind turbine response are calculated for surge, heave, and pitch motions along with the side-to-side, fore–aft, and yaw tower base bending moments. The transfer functions for surge, heave, and pitch motions for both spar-type and semisubmersible-type floaters are obtained using the fast code and the results are also compared with the results obtained in an experimental study. The long-term predictions of the most probable maximum values of motion amplitudes are used for design purposes, so as to guarantee the safety of the floating wind turbines against overturning in high waves and wind speed. The long-term distribution is carried out using North Atlantic wave data and the short-term floating wind turbine responses are represented using Rayleigh distributions. The transfer functions are used in the procedure to calculate the variances of the short-term responses. The results obtained for both spar-type and semisubmersible-type offshore floating wind turbine are compared, and the study will be helpful in the assessments of the long-term availability and economic performance of the spar-type and semisubmersible-type offshore floating wind turbine.