Enhancement of an innovative current turbine based on magnetic restoration

This doctoral thesis investigates the stability, efficiency, and fatigue life of an innovative turbine designed to extract energy from renewable flow resources through theoretical, numerical, and experimental studies. The turbine is based on the phenomenon of torsional galloping with magnetic restoration, introduced here as a novel concept. Energy extraction is enabled by the unstable dynamic behaviour of the turbine; consequently, stabilisation of the oscillatory motion must be avoided. To exploit this instability efficiently, a magnetic restoring torque is incorporated into the system. This magnetic restoration allows the oscillation amplitude of the turbine to be controlled, thereby limiting excessive vortex shedding and reducing energy losses. A linearized and a non-linear mathematical model were developed and solved. Their predictions were compared with computational simulations and experimental measurements obtained in a current channel. The stability analysis classifies the system response into spiral sink, spiral source, source, and saddle-type solutions and demonstrates that the regions exhibiting the greatest instability coincide with those of highest efficiency. The damping associated with the power take-off system was identified as the dominant parameter, with an optimum value of 0.45. Under these conditions, a maximum efficiency of 56.8% was obtained for a blade limit angle of 30°, a/c = 0.75, and Re = 15 × 10⁴. This corresponds to 95.78% of the Betz limit of 59.3%, with an estimated fatigue life of approximately 21 years. The proposed turbine therefore represents a promising concept for energy generation in remote regions without access to conventional electricity infrastructure and may contribute to the diversification of renewable energy technologies. Finally, the applicability of the concept is investigated for a river in the Amazon Basin. The resulting plant configuration is shown to satisfy the local electricity demand using a relatively small number of turbines and at a lower cost than the alternative configurations considered. The numerical simulations were conducted at the Institute for Fluid Dynamics and Ship Theory (FDS) at Hamburg University of Technology (TUHH), while the experimental investigations were carried out at the Laboratory of Waves and Currents (LOC) at COPPE/UFRJ.

Subjects

Torsional galloping

Magnetic restoration

Flow-induced oscillations

Hydrokinetic energy extraction

Stability analysis

Fatigue life

DDC Class

621: Applied Physics

333.7: Natural Resources, Energy and Environment

627: Hydraulic Engineering

Lizenz

https://creativecommons.org/licenses/by/4.0/

Publication version

publishedVersion

Name

(2026-10-16) ENHANCEMENT OF AN INNOVATIVE CURRENT TURBINE BASED ON MAGNETIC RESTORATION - TUHH VERSION.pdf

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26.76 MB

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Enhancement of an innovative current turbine based on magnetic restoration