Sloshing assessment of the LNG floating units with membrane type containment system where we are?

Malenica, S.,Diebold, L.,Kwon, S.H.,Cho, D.S. Elsevier Applied Science 2017 Marine structures Vol.56 No.-

The paper gives an overview of the current status of the methods and methodologies which are in use for the evaluation of the structural response induced by sloshing impacts. First the overall problem (seakeeping, sloshing, impacts, statistics...) is discussed and then the accent is put on the modeling of hydro-structure interactions which occur during the severe sloshing impacts in the tanks of the Liquefied Natural Gas (LNG) Carriers of membrane type. The main conclusion is that the sloshing assessment procedures are still under investigations and there are still no fully satisfactory methods and methodologies available to solve the problem fully consistently within the so called direct calculation approach. That is why, for the time being, a relatively simplified procedures are used in practice.

Hydro-structural issues in the design of ultra large container ships

Malenica, Sime,Derbanne, Quentin The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

The structural design of the ships includes two main issues which should be checked carefully, namely the extreme structural response (yielding & buckling) and the fatigue structural response. Even if the corresponding failure modes are fundamentally different, the overall methodologies for their evaluation have many common points. Both issues require application of two main steps: deterministic calculations of hydro-structure interactions for given operating conditions on one side and the statistical post-processing in order to take into account the lifetime operational profile, on the other side. In the case of ultra large ships such as the container ships and in addition to the classical quasi-static type of structural responses the hydroelastic structural response becomes important. This is due to several reasons among which the following are the most important: the increase of the flexibility due to their large dimensions (Lpp close to 400 m) which leads to the lower structural natural frequencies, very large operational speed (> 20 knots) and large bow flare (increased slamming loads). The correct modeling of the hydroelastic ship structural response, and its inclusion into the overall design procedure, is significantly more complex than the evaluation of the quasi static structural response. The present paper gives an overview of the different tools and methods which are used in nowadays practice.

Semi-Analytical Methods for Different Problems of Diffraction-Radiation by Vertical Circular Cylinders

Malenica, Sime Korean Society of Ocean Engineers 2012 International journal of ocean system engineering Vol.2 No.2

As in the other fields of mechanics, analytical methods represent an important analysis tool in marine hydrodynamics. The analytical approach is interesting for different reasons : it gives reference results for numerical codes verification, it gives physical insight into some complicated problems, it can be used as a simplified predesign tool, etc. This approach is of course limited to some simplified geometries (cylinders, spheres, ...), and only the case of one or more cylinders, truncated or not, will be considered here. Presented methods are basically eigenfunction expansions whose complexity depends on the boundary conditions. The hydrodynamic boundary value problem (BVP) is formulated within the usual assumptions of potential flow and is additionally simplified by the perturbation method. By using this approach, the highly nonlinear problem decomposes into its linear part and the higher order (second, third, ...) corrections. Also, periodicity is assumed so that the time dependence can be factorized i.e. the frequency domain formulation is adopted. As far as free surface flows are concerned, only cases without or with small forward speed are sufficiently simple to be solved semi-analytically. The problem of the floating body advancing in waves with arbitrary forward speed is far more complicated. These remarks are also valid for the general numerical methods where the case of arbitrary forward speed, even linearized, is still too difficult from numerical point of view, and "it is fair to say that there exists at present no general practical numerical method for the wave resistance problem" [9], and even less for the general seakeeping problem. We note also that, in the case of bluff bodies like cylinders, the assumptions of the potential flow are justified only if the forward speed is less than the product of wave amplitude with wave frequency.

Hydro-structural issues in the design of ultra large container ships

Sime Malenica,Quentin Derbanne 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

The structural design of the ships includes two main issues which should be checked carefully, namelythe extreme structural response (yielding & buckling) and the fatigue structural response. Even if the correspondingfailure modes are fundamentally different, the overall methodologies for their evaluation have many common points. Both issues require application of two main steps: deterministic calculations of hydro-structure interactions for givenoperating conditions on one side and the statistical post-processing in order to take into account the lifetime operationalprofile, on the other side. In the case of ultra large ships such as the container ships and in addition to the classicalquasi-static type of structural responses the hydroelastic structural response becomes important. This is due to severalreasons among which the following are the most important: the increase of the flexibility due to their large dimensions(Lpp close to 400 m) which leads to the lower structural natural frequencies, very large operational speed (> 20 knots)and large bow flare (increased slamming loads). The correct modeling of the hydroelastic ship structural response, andits inclusion into the overall design procedure, is significantly more complex than the evaluation of the quasi staticstructural response. The present paper gives an overview of the different tools and methods which are used in nowadayspractice

한일차세대학술포럼 제13회 국제학술대회 대학원생 공개패널토론

츠토미히로시,정은주,( Malenica Mirko Michel Misani ),김창진,이나가와미도리 동서대학교 일본연구센터 2017 次世代 人文社會硏究 Vol.13 No.-

Hydroelastic response of 19,000 TEU class ultra large container ship with novel mobile deckhouse for maximizing cargo capacity

임홍일,Nikola Vladimir,Sime Malenica,조대승 대한조선학회 2017 International Journal of Naval Architecture and Oc Vol.9 No.3

This paper is related to structural design evaluation of 19,000 TEU ultra large container ship, dealing with hydroelastic response, i.e. springing and whipping. It illustrates application of direct calculation tools and methodologies to both fatigue and ultimate strength assessment, simultaneously taking into account ship motions and her elastic deformations. Methodology for springing and whipping assessment within so called WhiSp notation is elaborated in details, and in order to evaluate innovative container ship design with increased loading capacity, a series of independent hydroelastic computations for container ship with mobile deckhouse and conventional one are performed with the same calculation setup. Fully coupled 3D FEM e 3D BEM model is applied, while the ultimate bending capacity of hull girder is determined by means of MARS software. Beside comparative analysis of representative quantities for considered ships, relative influence of hydroelasticity on ship response is addressed.

A comparison study of water impact and water exit models

Korobkin, Alexander,Khabakhpasheva, Tatyana,Malenica, Sime,Kim, Yonghwan The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

In problems of global hydroelastic ship response in severe seas including the whipping problem, we need to know the hydrodynamic forces acting on the ship hull during almost arbitrary ship motions. In terms of ship sections, some of them can enter water but others exit from water. Computations of nonlinear free surface flows, pressure distributions and hydrodynamic forces in parallel with the computations of the ship motions including elastic vibrations of the ship hull are time consuming and are suitable only for research purposes but not for practical calculations. In this paper, it is shown that the slamming forces can be decomposed in two components within three semi-analytical models of water entry. Only heave motion is considered. The first component is proportional to the entry speed squared and the second one to the body acceleration. The coefficients in these two components are functions of the penetration depth only and can be precomputed for given shape of the body. During the exit stage the hydrodynamic force is proportional to the acceleration of the body and independent of the body shape for bodies with small deadrise angles.

A comparison study of water impact and water exit models

Alexander Korobkin,Tatyana Khabakhpasheva,Sime Malenica,김용환 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

In problems of global hydroelastic ship response in severe seas including the whipping problem, we needto know the hydrodynamic forces acting on the ship hull during almost arbitrary ship motions. In terms of ship sections,some of them can enter water but others exit from water. Computations of nonlinear free surface flows, pressure distributionsand hydrodynamic forces in parallel with the computations of the ship motions including elastic vibrations ofthe ship hull are time consuming and are suitable only for research purposes but not for practical calculations. In thispaper, it is shown that the slamming forces can be decomposed in two components within three semi-analytical modelsof water entry. Only heave motion is considered. The first component is proportional to the entry speed squared and thesecond one to the body acceleration. The coefficients in these two components are functions of the penetration depthonly and can be precomputed for given shape of the body. During the exit stage the hydrodynamic force is proportionalto the acceleration of the body and independent of the body shape for bodies with small deadrise angles.

Global hydroelastic model for springing and whipping based on a free-surface CFD code (OpenFOAM)

Seng, Sopheak,Jensen, Jorgen Juncher,Malenica, Sime The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

The theoretical background and a numerical solution procedure for a time domain hydroelastic code are presented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solver where the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in a local floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frame undergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preserves the coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide the total fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forces and the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show that the VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responses accurately.

Global hydroelastic model for springing and whipping based on a free-surface CFD code (OpenFOAM)

Sopheak Seng,Jørgen Juncher Jensen,Šime Malenica 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.4

The theoretical background and a numerical solution procedure for a time domain hydroelastic code arepresented in this paper. The code combines a VOF-based free surface flow solver with a flexible body motion solverwhere the body linear elastic deformation is described by a modal superposition of dry mode shapes expressed in alocal floating frame of reference. These mode shapes can be obtained from any finite element code. The floating frameundergoes a pseudo rigid-body motion which allows for a large rigid body translation and rotation and fully preservesthe coupling with the local structural deformation. The formulation relies on the ability of the flow solver to provide thetotal fluid action on the body including e.g. the viscous forces, hydrostatic and hydrodynamic forces, slamming forcesand the fluid damping. A numerical simulation of a flexible barge is provided and compared to experiments to show thatthe VOF-based flow solver has this ability and the code has the potential to predict the global hydroelastic responsesaccurately.