Sara Muggiasca

Floating wind turbine platform motions can dynamically modulate wakes and alter turbine–turbine interactions within wind farms. While most previous studies have focused on isolated floating turbines, the aerodynamic coupling mechanisms in multi-turbine floating configurations remain insufficiently understood.This study experimentally investigates wake–rotor interactions induced by platform motion in a tandem floating wind turbine configuration subjected to prescribed harmonic surge. Two 1:150 scale DTU 10 MW turbines were tested in a wind tunnel under low-turbulence inflow, with systematic variation of motion reduced frequency (0.12–0.48) and relative phase between upstream and downstream platform motions. Aerodynamic loads, equivalent aerodynamic damping, wake velocity fields, and farm-level power were analyzed.The results show that reduced frequency governs wake modulation. At a reduced frequency of 0.48, surge motion generates coherent wake pulsations and enhanced wake recovery, leading to increased power of the downstream turbine. At a reduced frequency of 0.12, wake oscillations have smaller amplitude and do not significantly affect the time-averaged wake deficit or the farm power. The loads and aerodynamic damping of the downstream turbine depend strongly on the phase difference between turbine motions. In-phase motion maximizes thrust oscillations and damping, whereas anti-phase motion reduces the equivalent aerodynamic damping to approximately half of the upstream turbine value. Across all cases, wake interaction systematically decreases the aerodynamic damping of the downstream turbine.These findings highlight the importance of wake–motion synchronization in floating wind farms and its implications for both energy yield and system stability.

The integration of tilted photovoltaic strings on large, flat roofs, typical of industrial and commercial buildings, raises complex design challenges, particularly regarding wind-induced loads. This study presents a comprehensive wind tunnel investigation aimed at evaluating the aerodynamic effects on rooftop PV strings under various representative configurations and the correlation between characteristic geometric parameters such as tilt angle, bottom clearance, row spacing, and wind direction. Following a literature review, a detailed 1:10 scaled model with geometric adjustment capabilities was developed and eventually tested in a boundary-layer wind tunnel. High-resolution pressure measurements were processed to derive force and moment resultants normalised by reference wind pressure. Envelopes of force/moment resultants are presented for each representative geometric configuration and for each wind exposure angle. The results present severe variations in local wind actions, particularly significant at the strings’ free ends and for oblique wind angles. The severe underestimation of local wind loads by standard codes is discussed. The findings underline the importance of detailed wind-load assessment for both new constructions and retrofits, suggesting that reliance solely on code provisions might result in unsafe designs.

Floating Offshore Wind Turbines (FOWT) face control challenges due to right-half-plane zeros in the open-loop transfer function between blade pitch and rotor speed in above-rated conditions, which limit controller performance and can lead to closed-loop instability. Detuning the controller is a common workaround which sacrifices performance to ensure stability. Auxiliary feedback loops offer a promising alternative, enabling improved rotor speed regulation without compromising stability. However, while these loops enhance control potential, they also introduce additional dynamic interactions and coupling effects that significantly complicate system behavior. As a result, careful attention must be paid to gain scheduling to avoid adverse interactions and ensure robust performance. Existing gain scheduling strategies for multi-loop systems typically rely on robust stability margins, often neglecting performance-oriented design. This work proposes a novel gain scheduling method based on a linear quadratic regulator that enhances power tracking performance without modifying the existing Reference Open Source COntroller (ROSCO) architecture.

In the last twenty years, the global shipping transport demand has strongly increased (around 4% per year since the 1990s), together with the request for new green propulsion technologies to break down carbon emissions and face the costs deriving from the usage of conventional diesel fuels. Flettner rotors (hereafter: FRs) have been identified by several researchers as a promising solution to exploit wind energy on commercial ships, reducing fuel consumption. The present work presents a six-degree-of-freedom (6DOF) ship performance model set up to evaluate the best way of using a pair of Flettner rotors. The study analyses the performance of this propulsion system in consideration of weather and sea conditions, evaluating the related reduction in fuel consumption. A discussion about the economic and environmental advantages of the usage of FRs is provided, considering the costs linked to their installation and the new emission restrictions. Relevant results have been obtained for different routes, speed ranges and rotor dimensions while investigating the best Flettner rotor arrangement to minimise both the emissions and the installation cost payback period.

From an aerodynamic point of view, very large observation wheels are complex structures. Several parts are slender with bluff cross sections, and therefore wind–structure interaction effects can influence their dynamic behaviour. Vortex-induced vibrations (VIVs), wake-effects, galloping instability, wind–rain interactions and buffeting response must be considered and studied during the design of substructures such as the A-frames and spoke cables. Both wind-tunnel tests and numerical tools can be used to assess the expected vibration levels and eventually to design appropriate countermeasures. In this paper, the Ain Dubai observation wheel is taken as a test case to present a procedure that can be applied to verify and validate the design of such structures when considering the effects of natural wind. For the A-frame, which turned out to be prone to VIVs during wind-tunnel tests on a scaled model, tuned mass dampers are studied as mitigation devices; for the spoke cables, several parameters affecting their aerodynamics were investigated in a wind tunnel on a full-scale model: inclination angle, structural damping and LED equipment. The characterization of these effects allowed both the performance of the cable damping system to be assessed, and configurations that could not perform adequately to be discarded.

Experimental tests performed in a wind tunnel or in a natural laboratory represent a fundamental research tool to develop floating wind technologies. In order to obtain reliable results, the wind turbine scale model rotor must be designed so to obtain a fluid-structure interaction comparable to the one experienced by a real machine. This implies an aerodynamic design of the 3D blade geometry but, also, a structural project to match the main aeroelastic issues. For natural laboratory models, due to not controlled test conditions, the wind turbine rotor model must be checked also for extreme winds. The present paper will focus on all the strategies adopted to scale a wind turbine blade presenting two studied cases: the first is a 1:75 scale model for wind tunnel applications and the second a 1:15 model for natural laboratory tests.