Prediction of slamming pressure considering fluid-structure interaction. Part I: numerical simulations
Dac Dung Truong, Beom-Seon Jang, Han-Baek Ju, Sang Woong Han
Abstract
Marine structures are subjected to slamming loads characterised by high hydrodynamic pressure within short time durations. Such loads can cause local and global damages to structures. This paper, which is Part I in a series, reports a numerical investigation of slamming loads acting on flat stiffened plates and their dynamic response. The nonlinear explicit finite element code LS-Dyna with the Multi-Material Arbitrary Lagrangian-Eulerian (MMALE) solver was adopted to simulate the slamming impact on marine structures. The numerical method was validated by the relevant experimental data from the open literature in a comparison of slamming pressure and deflection data, as well as existing formulations. The Eulerian formulation was applied to describe the fluid flow, and a Lagrange formulation was employed to model flat stiffened plates. A penalty coupling algorithm was utilised to realise the fluid-structure interaction (FSI) between the plate and the fluid. Bilinear strain hardening with no strain-rate hardening and effect of the heat-affected zone (HAZ) were considered for the numerical simulation of the aluminum model, while nonlinear strain hardening and strain-rate hardening were adopted to verify the steel models. Effects of key influenced parameters such as water impact velocity, material behaviour, and air cushion on the slamming response were addressed accordingly. Additionally, a simulation of water hitting structure was proposed to investigate the slamming load characteristics acting on the bottom decks of offshore structures. As the next paper in this continuing series, Part II will present empirically derived formulations for prediction of slamming loads based on extensive parametric studies of actual scantlings of offshore structures, using the simulation methodology of water hitting proposed herein in Part I.