15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access Impact of structural flexibility on loads on tidal current turbines(2015) Arnold, Matthias; Biskup, Frank; Cheng, Po WenIn the development of tidal current turbines there are two common approaches regarding the required level of detail for load simulations. Those two are either to simulate the pressure field in detail with computational fluid dynamics (CFD) and assume a rigid geometry or to use a high fidelity structural model and simulate the hydrodynamic blade loads with the semi-empirical blade element momentum theory. Within the present research this simplification and the impact of fluid-structure-interaction (FSI) on the loads on tidal current turbines are analysed. Based on coupled CFD and multibody simulations the FSI is simulated for the Voith HyTide®1000-13 turbine. This method allows taking the detailed structure of the full turbine into account, while also simulating the detailed pressure field. Transient simulations of a representative point of operation are performed taking the structural flexibility of the tower, rotor blades, drivetrain and other components into account. This comparison is used to quantify the individual and combined effect of flexibilities on the loads and performance. Therefore, the Voith HyTide®1000-13 turbine is simulated within this research in varying levels of detail to analyse the required level of modelling detail for load simulations of tidal current turbines and increases the understanding of fluid-structure-interaction in tidal current turbine applications.Item Open Access Simulation of rotor-foundation-interaction on tidal current turbines with computational fluid dynamics(2013) Arnold, Matthias; Biskup, Frank; Matha, Denis; Cheng, Po WenIn this research the interaction of the rotor hydrodynamics with the foundation of a Tidal Energy Converter (TEC) are investigated. A detailed model of the turbine is built up and simulated with Computational Fluid Dynamics (CFD). The results of these simulations are used to compare the 4 load states of up- and downstream, below and above rated operation with respect to the rotor performance coefficients. The paper concludes with a comparison to results of simplified models and shows that the interaction can be simulated by an empirical approach.Item Open Access Load reduction potential of variable speed control approaches for fixed pitch tidal current turbines(2015) Arnold, Matthias; Biskup, Frank; Cheng, Po WenThe present paper compares control strategies for fixed pitch Tidal Current Turbines and introduces the underspeed control technique. The state of the art approach of overspeed control for fixed pitch turbine increases the tip speed ratio to limit the power output of the turbine. This leads to a high fatigue loading as the number of load cycles increases and requires a specific rotor design not to increase the thrust coefficient as well. The underspeed controller on the other side reduces the tip speed ratio resulting in a reduced thrust coefficient and a reduced number of load cycles. However, this point of operation is unstable based on the characteristic curves of the rotor and needs to be stabilized by the controller. The basic structure of the controller as well as the calculated stability limits will be shown in the paper. Further, the performance of the underspeed controller regarding loads is compared to state of the art fixed and variable pitch controllers. The paper concludes with an analysis of the impacts on the turbine design and further potential and issues arising with the underspeed control approach.