Operational modal analysis of a spar-type floating platform using frequency domain decomposition method

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

Progress on the experimental set-up for the testing of a floating offshore wind turbine scaled model in a field site

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

Simulation of Water Sensitive Papers for Spray Analysis

Aim of this study was to simulate the water sensitive paper (WSP) behaviour for estimate the unitary spray deposition on the target at varying spray features and target coverage.  WSP images were produced assuming some simplifying hypotheses: spherical drops and circular stains randomly placed on the images. Sprays were described in terms of probability distribution function (PDF) of drop size (log-normal and Rosin-Rammler), coefficient of variation of diameters (CV), arithmetic mean diameter (AMD), and volume median diameter (VMD).  The results from the simulations showed that the overlap between stains was independent of spray features: when the percentage of covered surface of WSP images ranged from 4.7 up to 61.6%, the overlap between stains ranged from 0.3 up to 33.4%.   On the contrary, unitary deposit (volume per square centimetre, mL cm-2) and particle density (number of distinct particles per square centimetre, cm-2) could be obtained from the percentage of covered surface if CV, AMD, VMD and PDF were known.  However, assuming as spray parameter the VMD, the drop size distribution had almost no effect on the unitary deposit: with the same percentage of covered surface, the Rosin-Rammler PDF provided an estimate of the unitary deposit higher than log-normal distribution between 5 and 7% only

An exact approach to the dynamics of locally-resonant beams

Abstract This paper presents an exact analytical approach to calculate the dynamic response of elastic beams with periodically-attached resonators, generally referred to as locally-resonant beams. Showing that a typical resonator is equivalent to an external constraint, whose reaction force on the beam depends on the deflection of the application point through a pertinent frequency-dependent stiffness, the beam-resonators coupled system is handled using only the beam motion equation, with Dirac's deltas modelling the shear-force discontinuities associated with the reaction forces of the resonators. This is the basis to tackle the dynamics of infinite as well as finite beams, the first by a transfer matrix method to calculate frequency band gaps, the second by a generalized function approach. The dynamics of the finite beam is studied in frequency and time domains deriving the exact frequency response and the exact modal response, including modal frequency and impulse response functions. The proposed approach is formulated for arbitrary number of resonators and loads, and applies for both non-proportional and proportional damping

on the moving multi loads problem in discontinuous beam structures with interlayer slip

Abstract This contribution proposes an efficient approach to the moving multi-loads problem on two-layer beams with interlayer slip and elastic translational supports. The Euler-Bernoulli hypothesis is assumed to hold for each layer separately, and a linear constitutive relation between the horizontal slip and the interlaminar shear force is considered. It is shown that, using the theory of generalized functions to treat the discontinuous response variables, exact eigenfunctions can be derived from a characteristic equation built as determinant of a 6 x 6 matrix. Building pertinent orthogonality conditions for the deflection eigenfunctions, a closed-form analytical response is established in the time domain. The proposed procedure is illustrated for a two-layer beam with interlayer slip, elastically supported at the center and acted upon by moving multi-loads

Binding Properties of a Dinuclear Zinc(II) Salen-Type Molecular Tweezer with a Flexible Spacer in the Formation of Lewis Acid-Base Adducts with Diamines

In this paper we report the binding properties, by combined 1H NMR, optical absorption, and fluorescence studies, of a molecular tweezer composed of two Zn(salen)-type Schiff-base units connected by a flexible spacer, towards a series of ditopic diamines having a strong Lewis basicity, with different chain length and rigidity. Except for the 1,2-diaminoethane, in all other cases the formation of stable 1:1 Lewis acid-base adducts with large binding constants is demonstrated. For α,ω-aliphatic diamines, binding constants progressively increase with the increasing length of the alkyl chain, thanks to the flexible nature of the spacer and the parallel decreased conformational strain upon binding. Stable adducts are also found even for short diamines with rigid molecular structures. Given their preorganized structure, these latter species are not subjected to loss of degrees of freedom. The binding characteristics of the tweezer have been exploited for the colorimetric and fluorometric selective and sensitive detection of piperazine

Mass Balance as Green Economic and Sustainable Management in WEEE Sector

Abstract This study investigates the treatment procedures of the Large House Hold Appliance to describe the production of secondary raw material within the Waste of Electric and Electronic Equipment (WEEE) sector in step with the Circular Economy model. Drawing on the modern accounting system, the project developed a perspective, which highlights accounting technologies (i.e. Environmental Accounting, sustainable performance indicators, Mass Balance) as new adaptive management tools for sustainable firms. The theoretical arguments shown by a longitudinal case study proposes a conceptual framework of the e-waste manage within treatment plants in the Sicilian context. The results demonstrate a percentage analysis by waste fraction of all materials recovered which can be re-use. Then, the recognition of critical raw materials identifies the end of west in implementing a competitive advantage for business growth

Stochastic response of a fractional vibroimpact system

The paper proposes a method to investigate the stochastic dynamics of a vibroimpact single-degree-of-freedom fractional system under a Gaussian white noise input. It is assumed that the system has a hard type impact against a one-sided motionless barrier, which is located at the system's equilibrium position; furthermore, the system under study is endowed with an element modeled with fractional derivative. The proposed method is based on stochastic averaging technique and overcome the particular difficulty due to the presence of fractional derivative of an absolute value function; particularly an analytical expression for the system's mean squared response amplitude is presented and compared with results obtained by numerical simulations