Chaired by: F. Porté-Agel, J. Jonkman
10:30
Modern methods to investigate the stability of a pitching floating platform wind turbine
Matthew Lennie | TU Berlin | Germany
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Matthew Lennie | TU Berlin | Germany
Matthew Lennie | Germany
David Marten | Germany
George Pechlivanoglou | Germany
Christian Navid Nayeri | Germany
Christian Oliver Paschereit | Germany
The QBlade implementation of the Lifting Line Free VortexWake method (LLFVW) was tested in conditions analogous to foating platform motion. Comparisons against two in- dependent test cases, using a variety of simulation methods show excellent agreement in thrust forces, rotor power, blade forces and rotor plane induction. Along with the many verifications already undertaken in literature, it seems that the code performs solidly even in these challenging cases. Further to this, the key steps are presented from a new formulation of the instantaneous aerodynamic thrust damping of a wind turbine rotor. A test case with harmonic platform motion and collective pitch is used to demonstrate how combining such tools can lead to better understanding of aeroelastic stability.
10:50
Periodic stability assessment of a exible hub connection for load reduction on two-bladed wind turbines
Birger Luhmann | University of Stuttgart | Germany
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Birger Luhmann | University of Stuttgart | Germany
Po Wen Cheng | Germany
The periodic stability of an innovative load reduction system for two-bladed wind turbines is investigated using Floquet theory. The load reduction system introduces an additional cardanic degree of freedom between the hub mount and the nacelle carrier flange. A reduced rotor model is considered to analyze the time-variant behavior as a function of rotor shapes and design parameters. The linearized, homogeneous system equations of motion indicate a dependance of the rotor shape and the periodic system stability. Due to the time-variance of the asymmetric rotor the Floquet multipliers are derived to determine system stability and the dominant periodic coefficients. Gyroscopic effects are the reason for a stabilization of disc-like rotors, whereas a cylindrical, two-bladed rotor assembly is in general unstable. The introduction of an additional spring-damper coupling is a possibility to stabilize such configurations, but results show that resonance phenomena have to be accounted for.
11:10
Comparison of linear and non-linear blade model predictions in Bladed to measurement data from GE 6MW wind turbine
William Collier | DNV GL | United Kingdom
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William Collier | DNV GL | United Kingdom
Jose-Maria Milian Sanz | United Kingdom
The length and flexibility of wind turbine blades are increasing over time. Typically, the dynamic response of the blades is analysed using linear models of blade deflection, enhanced by various ad-hoc non-linear correction models. For blades undergoing large deflections, the small deflection assumption inherent to linear models becomes less valid. It has previously been demonstrated that linear and non-linear blade models can show significantly different blade response, particularly for blade torsional deflection, leading to load prediction differences. There is a need to evaluate how load predictions from these two approaches compare to measurement data from the field. In this paper, time domain simulations in turbulent wind are carried out using the aero-elastic code Bladed with linear and non-linear blade deflection models. The turbine blade load and deflection simulation results are compared to measurement data from an onshore prototype of the GE 6MW Haliade turbine.
11:30
FAST modularization framework for wind turbine simulation: full-system linearization
Dr. Jason Jonkman | NREL | United States
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Dr. Jason Jonkman | NREL | United States
Bonnie Jonkman | United States
Michael Sprague | United States
The wind engineering community relies on multiphysics engineering software to run nonlinear time-domain simulations e.g. for design-standards-based loads analysis. Although most physics involved in wind energy are nonlinear, linearization of the underlying nonlinear system equations is often advantageous to understand the system response and exploit well-established methods and tools for analyzing linear systems. This paper presents the development and verification of the new linearization functionality of the open-source engineering tool FAST v8 for land-based wind turbines, as well as the concepts and mathematical background needed to understand and apply it correctly.
11:50
Aeroelastic Simulation of Multi-MW Wind Turbines using a Free Vortex Model Coupled to a Geometrically Exact Beam Model
Joseph Saverin | TU Berlin | Germany
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Joseph Saverin | TU Berlin | Germany
Juliane Peukert
David Marten | Germany
Christian Navid Nayeri | Germany
Georgios Pechlivanoglou | Germany
Christian Oliver Paschereit | Germany
The current paper investigates the aeroelastic modelling of large, flexible multi-MW wind turbine blades. Most current performance prediction tools make use of the Blade Element Momentum (BEM) model, based upon a number of simplifying assumptions that hold only under steady conditions. This is why a lifting line free vortex wake (LLFVW) algorithm is used here to accurately resolve unsteady aerodynamics. A coupling to the structural analysis tool BeamDyn, based on geometrically exact beam theory, allows for time-resolved aeroelastic simulations with highly deflected blades including bend-twist coupling. Predictions of blade loading and deformation for rigid and flexible blades are analysed with reference to different aerodynamic and structural approaches. The emergency shutdown procedure is chosen as an examplary design load case causing large deflections to place emphasis on the influence of structural coupling and demonstrate the necessity of high fidelity structural models.
12:10
Real-time hybrid simulation technique for performance evaluation of full-scale sloshing dampers in wind turbines
Dr. Zili Zhang | Aarhus University | Denmark
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Dr. Zili Zhang | Aarhus University | Denmark
Biswajit Basu | Denmark
Søren R.K. Nielsen | Denmark
As a variation of the pseudodynamic testing technique, the real-time hybrid simulation (RTHS) technique is executed in real time, thus allowing investigation of structural systems with rate-dependent components. In this paper, the RTHS is employed for performance evaluation of full-scale liquid sloshing dampers in multi-megawatt wind turbines, where the tuned liquid damper (TLD) is manufactured and tested as the physical substructure while the wind turbine is treated as the numerical substructure and modelled in the computer using a 13-degree-of-freedom (13-DOF) aeroelastic model. Wind turbines with 2 MW and 3 MW capacities have been considered under various turbulent wind conditions. Extensive parametric studies have been performed on the TLD, e.g., various tuning ratios by changing the water level, TLD without and with damping screens (various mesh sizes of the screen considered), and TLD with flat and sloped bottoms. The present study provides useful guidelines for employing sloshing dampers in large wind turbines, and indicates huge potentials of applying RTHS technique in the area of wind energy.