Misura dei parametri fondamentali dei treni d\u2019onde regolari generabili presso la Vasca del DINMA: Analisi di incertezza e propagazione degli errori sulla calibrazione dell\u2019ondogeno

In questa memoria vengono riportati i risultati della nuova taratura eseguita sulla qualit\ue0 delle onde generate nella Vasca Idrodinamica dell'Universit\ue0 di Trieste in conseguenza dell'aggiornamento della movimentazione dell'ondogeno. I risultati si riferiscono all'analisi della composizione armonica delle onde generate, all'analisi di incertezza ed alla formulazione di una nuova formulazione della legge di controllo dell'ondogeno, per la quale si fornisce un codice di calcolo dedicato

On the Side Wall Effect on the Non-Linear Wave Loads on a Tlp Like Structure in a Wave Tank: Analysis of the Non-Linear Near Trapping

This paper shows some numerical results obtained at DINMA on the fully nonlinear interaction of regular waves with four bottom-mounted circular cylinders [D\u2019Este et al. 2001]. The phenomenon of interest is the so-called near trapping, i.e. the large magnification of the amplitude of the free surface elevation and induced pressures in the zone delimited by the cylinders surface. Linear theory [Linton & Evans, 1990] and experiments [Contento et al. 2000] show that this amplification depends strongly on the ratios of the column radius to the incident wavelength (ka parameter) and of the column radius to the side of the square (a/d parameter). In this specific case we analyse the ka condition that leads to extremely large oscillations of the second Fourier components of the free surface elevation in the inner zone and of the related pressure [Malenica et al., 1999] even in small amplitude incident waves. In particular the interest is focused on the behaviour of the higher order terms of the forces and run-up for two different configurations of the wave tank while keeping the same hydrodynamic parameters (ka, a/d). From the preliminary results shown in the present work, it seems that first order in-line terms are only weakly affected by the dimensions of the basin whereas the first order side force on the lateral cylinder shows evident interference effects. At the same time, the amplitude of the second order terms of the forces show a smoother variation with time for the larger basin

Experimental Study on a Spread Catenary Mooring for FPSO

This paper summarises the main results of experimental tests conducted at the Danish Hydraulic Institute in the frame of the EU-TMR-LSF project \u201cA New Concept of Catenary Mooring System for FPSO\u201d. The main interest of this research project is the analysis of the behaviour of a proposed mooring system for FPSO well suited for weather conditions characterised by a dominant swell and current and by a moderate almost perpendicular local sea and wind. The basic idea of this mooring design is to join the best characteristics of the turret and spread mooring systems to allow the FPSO to move within a specified offset so that the wave loads on the lines and on the vessel can be minimised. The experiments and the related analysis refer to the dynamic behaviour of the FPSO alone and FPSO+Shuttle tanker during offloading, in extreme and operational weather conditions respectively. In the case with the FPSO+Shuttle tanker the tension on the hawser is analysed too

Numerical Study on the Non-linear Behaviour of Steep Isolated Unidirectional Waves

This paper presents some results of a study on the non-linear features of steep isolated 2D waves conducted at the Dept. of Naval Architecture, Ocean and Environmental Engineering of the University of Trieste in the frame of a wider research project financed by CETENA SpA on the wave loads on ships and marine structures in severe sea conditions. The analysis is here conducted by numerical simulations, thus solving the fully non-linear flow field by means of a BEM technique, and specifically it regards the non-linear effects deriving from the wave-wave interaction due to the frequency focusing of the component waves in a given spectrum [Codiglia, 2002; Contento et al., 2001]. It is shown that the shape of the wave spectrum computed at different stations in the direction of propagation is modified as a consequence of the nonlinear interaction of the component waves. In particular new high frequencies appear at positions close to the focusing station with non-negligible amplitudes. Moreover the highest wave is magnified by several unit percent (up to 15%) compared to simple linear predictions and the phase speed of the new high frequency components doesn\u2019t fulfil the dispersion relation but it is locked to the phase speed of the highest component in the discrete input spectrum. Each numerical result here shown is supported by analogous experimental data presented by Chaplin [1996] and Chaplin et al. [1997

On the Side Wall Effects on the Nonlinear Wave Loads on a TLP-like Structure in a Wave Tank: Analysis of the Nonlinear Near-trapping

This paper shows some numerical results obtained at DINMA on the fully nonlinear interaction of regular waves with four bottom-mounted circular cylinders [D\u2019Este et al. 2001]. The phenomenon of interest is the so-called near trapping, i.e. the large magnification of the amplitude of the free surface elevation and induced pressures in the zone delimited by the cylinders surface. Linear theory [Linton & Evans, 1990] and experiments [Contento et al. 2000] show that this amplification depends strongly on the ratios of the column radius to the incident wavelength (ka parameter) and of the column radius to the side of the square (a/d parameter). In this specific case we analyse the ka condition that leads to extremely large oscillations of the second Fourier components of the free surface elevation in the inner zone and of the related pressure [Malenica et al., 1999] even in small amplitude incident waves. In particular the interest is focused on the behaviour of the higher order terms of the forces and run-up for two different configurations of the wave tank while keeping the same hydrodynamic parameters (ka, a/d). From the preliminary results shown in the present work, it seems that first order in-line terms are only weakly affected by the dimensions of the basin whereas the first order side force on the lateral cylinder shows evident interference effects. At the same time, the amplitude of the second order terms of the forces show a smoother variation with time for the larger basin