Wave impact loads: The role of the flip-through

Lugni, Claudio; Brocchini, Maurizio; Faltinsen, Odd M.

doi:10.1063/1.2399077

Cited by 157 publications

(120 citation statements)

References 11 publications

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“…Scaling laws for impacts with a significant amount of trapped air still need to be developed. Describing the phenomena, as done by Lugni et al [96] and Bogaert et al [18], is a first step towards this goal. Possibly, the final solution is a CFD method where all relevant physical parameters are properly modelled so that separate calculations for the model and full scale can be made.…”

Section: Remaining Challengesmentioning

confidence: 99%

Slamming of ships: where are we now?

Kapsenberg

2011

Phil. Trans. R. Soc. A.

112

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Literature published on the problem of ship slamming in waves is reviewed from the point of view of someone working at a ship research institute. Such an institute is confronted with rather practical questions regarding the acceptability of certain design parameters such as the acceptable amount of bow flare angle for use at sea. The importance of these questions is illustrated by noting that actual slamming or the presumed danger of slamming is the main reason for ship operators to reduce speed or to change heading. The review shows that such questions cannot yet be answered. The problem of the local effect of the impact is very complicated owing to the importance of air inclusions, bubbles in the water, compressibility of water and cavitation effects. Only a computational method properly including all these effects will give an accurate answer; also model tests will not be capable of doing this, if only because the methods to extrapolate the results of models to full scale are not yet developed. The problem of the global response of the ship to a wave impact is closer to being solved. A two-stage approach is proposed, consisting of a computational fluid dynamics method for individual impacts and an approximate method to be included in long-term simulations. However, to arrive at a realistic longterm distribution, one has to account for the seamanship of the captain; avoiding the worst conditions or adapting the ship speed and course has a large effect on the actual extremes. Research on this topic has hardly begun.

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Section: Remaining Challengesmentioning

confidence: 99%

Slamming of ships: where are we now?

Kapsenberg

2011

Phil. Trans. R. Soc. A.

112

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“…For example, when the impact angle between liquid and wall is small, gas entrapment may happen leading to gas compression and its interaction with the free surface. 4,5 In contrast, for an incipient breaking wave approaching a vertical wall, flip-through events 6 or flat impacts may occur causing localized and large loads without any gas-entrapment.…”

Section: Introductionmentioning

confidence: 99%

“…The previous paper by Lugni et al, 6 has emphasized how the maximum pressure at a fixed point of the impact area is a poor indicator for the maximum load, because of the extremely local behavior of the impact phenomena. In the present paper, the strain distribution along a vertical deformable aluminium plate inserted in the rigid vertical wall of a sloshing tank has been measured in model tests to characterize the dynamical features of the local loads.…”

Section: Introductionmentioning

confidence: 99%

“…The evolution of a flip-through event [6] upon a vertical, deformable wall during shallow-water sloshing in a 2D tank is analyzed, with specific focus on the role of hydroelasticity. An aluminium plate, whose dimensions are Froude-scaled in order to reproduce the first wet natural frequency associated with the typical structural panel of a Mark III containment system, is used.…”

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confidence: 99%

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Hydroelastic slamming response in the evolution of a flip-through event during shallow-liquid sloshing

et al. 2014

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The evolution of a flip-through event [6] upon a vertical, deformable wall during shallow-water sloshing in a 2D tank is analyzed, with specific focus on the role of hydroelasticity. An aluminium plate, whose dimensions are Froude-scaled in order to reproduce the first wet natural frequency associated with the typical structural panel of a Mark III containment system, is used. (Mark III Containment System is a membrane-type tank used in the Liquefied Natural Gas (LNG) carrier to contain the LNG. A typical structural panel is composed by two metallic membranes and two independent thermal insulation layers. The first membrane contains the LNG, the second one ensures redundancy in case of leakage.) Such a system is clamped to a fully rigid vertical wall of the tank at the vertical ends while being kept free on its lateral sides. Hence, in a 2D flow approximation the system can be suitably modelled, as a double-clamped Euler beam, with the Euler beam theory. The hydroelastic effects are assessed by cross-analyzing the experimental data based both on the images recorded by a fast camera, and on the strain measurements along the deformable panel and on the pressure measurements on the rigid wall below the elastic plate. The same experiments are also carried out by substituting the deformable plate with a fully stiff panel. The pressure transducers are mounted at the same positions of the strain gauges used for the deformable plate. The comparison between the results of rigid and elastic case allows to better define the role of hydroelasticity. The analysis has identified three different regimes characterizing the hydroelastic evolution: a quasi-static deformation of the beam (regime I) precedes a strongly hydroelastic behavior (regime II), for which the added mass effects are relevant; finally, the free-vibration phase (regime III) occurs. A hybrid method, combining numerical modelling and experimental data from the tests with fully rigid plate is proposed to examine the hydroelastic effects. Within this approach, the measurements provide the experimental loads acting on the rigid plate, while the numerical solution enables a more detailed analysis, by giving additional information not available from the experimental tests. More in detail, an Euler beam equation is used to model numerically the plate with the added-mass contribution estimated in time. In this way the resulting hybrid method accounts for the variation of the added mass associated with the instantaneous wetted length of the beam, estimated from the experimental images. Moreover, the forcing hydrodynamic load is prescribed by using the experimental pressure distribution measured in the rigid case. The experimental data for the elastic beam are compared with the numerical results of the hybrid model and with those of the standard methods used at the design stage. The comparison against the experimental data shows an overall satisfactory prediction of the hybrid model. The maximum peak pressure predicted by the standard methods agrees with the result of th...

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“…Marino et al [5], [6] coupled the aero-elastic model with non-linear wave theory to solve the dynamic force on the structure. It was found by the studies of Marino and Lugni [5]- [7] that the wave force and local pressure increase in a short period of time when wave breaking near the support structure of the wind turbine. Marino et al [8] employed the nonlinear wave theory and statistical method to analyze the force on the wind turbine for a long time.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Analysis for a Jacket-Type Support Structure of the Offshore wind Turbine

Chen

Lin

et al. 2016

MATEC Web Conf.

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Abstract. In the present study, the hydrodynamic load due to extreme external condition, such as typhoon, on the offshore wind turbine (OWT) has been investigated by numerical simulations. The hydrodynamic loads including the sea current, regular and irregular wave on the structure are taken into account. The sea current is considered with the constant flow speed, whereas the wave is considered as regular and irregular based on the observed data at considered locations. Using Splash3D, a three-dimensional numerical model is developed for performing the force evaluation of the OWT. Multi-phase flow is evaluated by the volume of fraction (VOF) model, and the turbulent flow is described by the large-eddy-simulation (LES) model. It can be deduced that using the regular wave as the hydrodynamic load for the evaluation of the OWT system will vanish some instantaneous extreme wave. In the case of using the irregular wave, the instantaneous extreme wave is also taken into account. With such more practical hydrodynamic load, the average force for the case of irregular wave is 64% larger than that of the regular wave.

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Wave impact loads: The role of the flip-through

Cited by 157 publications

References 11 publications

Slamming of ships: where are we now?

Slamming of ships: where are we now?

Hydroelastic slamming response in the evolution of a flip-through event during shallow-liquid sloshing

Hydrodynamic Analysis for a Jacket-Type Support Structure of the Offshore wind Turbine

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