A reduced order model for structural response of the Mark III LNG cargo containment system

Abstract

Highly varying sloshing loads are a superposition of load components resulting from a sequence of different physical phenomena. However, not all features of spatial and temporal variations of sloshing loads and associated phenomena are equally important when failure of structure is considered. Therefore, the prediction of sloshing loads should be focused on those load components which lead to failure. These components can be found by employing a structural model, which should be fast computationally considering the huge number of possible sloshing loads. This paper presents a reduced order model based on the beam-foundation model which is derived for the Mark-III cargo containment system. The model is validated against a detailed finite element model and it conservatively predicts the stresses at failure locations. The calculation time using the model is approximately two orders smaller in comparison to a finite element model computation, which allows the model to be applied for finding governing load components and associated physical phenomena.

A reduced order model for FSI of tank walls subject to wave impacts during sloshing

“…The CSS is simplified to a mass-spring system following [4], giving an equation of the following form:…”

“…On the inside of the tank a stainless steel membrane is fitted to keep the LNG inside, and a secondary membrane is fitted between the foam layers for redundancy. In order to minimize thermal stresses, relaxation grooves are cut just above the secondary membrane, creating 'subpanels' of 340 by 340 mm which are to a large extent uncoupled [4]. Note that Fig.…”

“…If either of these two failure modes occur, then there is a high probability that also one of the membranes will fail, which is to be avoided at all times. A reduced order model for the onset on indentation failure is presented in [4], based on [20] and [24]. Prediction of the structural response can be significantly sped up using such a reduced order model, possibly leading to great simplification of the coupled problem.…”

“…In this paper the coupling between the CCS and a wave impact is investigated on the subpanel level. The subpanel is represented by the beam-foundation model proposed in [4], which predicts the response to the first vibration mode of the CCS. ELP 2: 'building jet' is chosen as load case, because it is expected to give a response on the length and time scale as the structure.…”

A compressible two-phase flow model for pressure oscillations in air entrapments following green water impact events on ships

“…By entrapping an air pocket between the water and the structure, the pocket can have a cushioning effect on the peak pressure on the one hand [5,27]. On the other hand, it can give an increase of the acting force on the structure during a wave impact [5,26] and the pressure oscillations in the air pocket can increase pressure levels on the structure being impacted [27] as well as induce resonant fluid-structure interaction [3]. Naval architects are interested in determining these pressures for design.…”