Papers by Carlo Sebastiano Ruzzo
Vibration Control of Large Floating Offshore Structures by Means of Damping Plates: A Case Study
Lecture Notes in Civil Engineering, 2019
Large floating multi-purpose platforms are interesting and emerging concepts in terms of envisage... more Large floating multi-purpose platforms are interesting and emerging concepts in terms of envisaged future development in the offshore engineering. The investigation on the hydrodynamic behaviour of such structures plays an important role in their characterization. In particular, vibration control and motion reduction of the platform may be crucial for its operation since most of the renewable energy converters cannot cater to large support motions (e.g. wind turbines, photovoltaic plants and OWC wave energy converters). With this as the background, a small-scale open-sea experimental investigation on a barge structure has been carried out in the Natural Ocean Engineering Laboratory (NOEL) in Reggio Calabria, Italy. The barge was equipped with removable vertical plates in order to investigate their effects on the structure dynamics and their optimal configuration, in terms of its motion attenuation. In addition, a numerical model using the commercial software Ansys AQWA (v. 16.1) is used to investigate its dynamic effects for five different configurations of the plates both in the time and in the frequency domains.
Energies, 2020
Output-only methods are widely used to characterize the dynamic behavior of very diverse structur... more Output-only methods are widely used to characterize the dynamic behavior of very diverse structures. However, their application to floating structures may be limited due to their strong nonlinear behavior. Therefore, since there is very little experience on the application of these experimental tools to these very peculiar structures, it is very important to develop studies, either based on numerical simulations or on real experimental data, to better understand their potential and limitations. In an initial phase, the use of numerical simulations permits a better control of all the involved variables. In this work, the Covariance-driven Stochastic Subspace Identification (SSI-COV) algorithm is applied to numerically simulated data of two different solutions to Floating Offshore Wind Turbines (FOWT) and for its capability of tracking the rigid body motion modal properties and susceptibility to different modeling restrictions and environmental conditions tested. The feasibility of ap...
Journal of Marine Science and Technology, 2018
The investigation of the interaction of floating structures with very high waves, also known as f... more The investigation of the interaction of floating structures with very high waves, also known as freak or rogue waves, is of crucial importance for the analysis of their ultimate design conditions. The representation of such waves is usually achieved through computationally intensive numerical simulations. In this paper, a deterministic approach is proposed, to represent extreme wave groups in the space-time domain. The free surface profile for a Gaussian sea is obtained by means of the Quasi-Determinism theory, and the corresponding dynamic response of a spar-type support for floating offshore wind turbines in parked rotor conditions is analyzed. The Quasi-Determinism theory and the nonlinear equation of motion of the structure are coupled through an in-house time-domain numerical code. Wave forces and structure motions in surge, heave and pitch are obtained. A parametric analysis is carried out to investigate the effects of the criteria used for the definition of the extreme wave, its position of occurrence and the initial conditions in terms of body motions. The results obtained give a clear insight into the physics of the wave-structure interaction phenomenon for extremely high waves in Gaussian seas and allow to identify a few load combinations, corresponding to the severest wave conditions for the floating structure. Keywords Extreme waves in Gaussian seas • Quasi-determinism theory • Floating offshore wind turbines • Spar
Wind Engineering, 2016
This document describes design and realization of a small-scale field experiment on a 1:30 model ... more This document describes design and realization of a small-scale field experiment on a 1:30 model of spar floating support structure for offshore wind turbines. The aim of the experiment is to investigate the dynamic behaviour of the floating wind turbine under extreme wave and parked rotor conditions. The experiment has been going on in the Natural Ocean Engineering Laboratory of Reggio Calabria (Italy). In this article, all the stages of the experimental activity are presented, and some results are shown in terms of motions and response amplitude operators. Finally, a comparison with corresponding results obtained using ANSYS AQWA software package is shown, and conclusions are drawn. The presented experimental set-up seems promising to test offshore floating structures for marine renewable energy at a relatively large scale in the Natural Ocean Engineering Laboratory field site.
Energies, 2016
System identification of offshore floating platforms is usually performed by testing small-scale ... more System identification of offshore floating platforms is usually performed by testing small-scale models in wave tanks, where controlled conditions, such as still water for free decay tests, regular and irregular wave loading can be represented. However, this approach may result in constraints on model dimensions, testing time, and costs of the experimental activity. For such reasons, intermediate-scale field modelling of offshore floating structures may become an interesting as well as cost-effective alternative in a near future. Clearly, since the open sea is not a controlled environment, traditional system identification may become challenging and less precise. In this paper, a new approach based on Frequency Domain Decomposition (FDD) method for Operational Modal Analysis is proposed and validated against numerical simulations in ANSYS AQWA v.16.0 on a simple spar-type structure. The results obtained match well with numerical predictions, showing that this new approach, opportunely coupled with more traditional wave tanks techniques, proves to be very promising to perform field-site identification of the model structures.
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Papers by Carlo Sebastiano Ruzzo