Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Simulation and validation of three-dimensional water entry of lifeboats using smoothed particle
hydrodynamics with adaptive particle refinement
Hong-Guan Lyu1,2, Peng-Nan Sun1,2,*, Xiao-Rui Yin1,2, Xiao-Ting Huang1,2, A-Man Zhang3
1 School of Ocean Engineering and Technology, Sun Yat-sen University, Zhuhai, China
2 Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
3 College of Shipbuilding Engineering, Harbin Engineering University, Harbin, Chinatransforming the model measurements into full-scale data (Lugni et al.,2021). Secondly, physical tests are always expensive and several
extreme case conditions are hard to be reproduced in a laboratory.
Therefore, the technique of Computational Fluid Dynamics (CFD) can
be a more feasible strategy in engineering designs.

ABSTRACTThe hydrodynamic performance of lifeboats is critical for the safety ofpassengers since several complex fluid-structure interaction phenomena
could occur during the water entry phase. This paper, within a fully 3D
Smoothed Particle Hydrodynamics (SPH) framework, is dedicated toinvestigating the hydrodynamic performance of a lifeboat by comparing
with the reference results obtained via a Finite Volume (FV) solver. At
first, the adopted 3D SPH model is briefly introduced with a multiresolution consideration. Subsequently, a water entry benchmark of acylinder is performed to validate the accuracy and stability of the utilized
SPH model. Furthermore, the motion characteristics of the lifeboat withdifferent water entry angles are investigated and discussed in detail. Inparticular, a comparative study is performed to assess the feasibility andaccuracy of the SPH and FV methods in solving such problems. It isclearly demonstrated that thanks to its inherent Lagrangian nature, theSPH method can accurately capture the splashing jets and droplets during
the water entry of the lifeboat. It is also indicated that for such problems,
the air phase could somewhat affect the local flow fields behind thelifeboat, whereas it poses limited effects on the overall hydrodynamic
performance of the lifeboat.

In terms of CFD, traditional Eulerian mesh-based methods, e.g. Finite
Volume (FV), have been widely adopted to simulate the water entry
problems for different simple objects such as cylinders (Hou et al., 2018),
wedges (Wang et al., 2021) and spheres (Shen et al., 2022), whereas
applying them for solving the water entry dynamics of complex
structures such as lifeboats is relatively rare. In fact, some researchers
have been devoted to this topic using the mature commercial package
named STAR-CCM+ (Tregde and Nestegård, 2014; Tregde, 2015;
Huang et al., 2021), while it can be found from these works that the water
surface evolutions cannot be accurately simulated due to the inherent
mass-non-conservation property of the FV method. Besides, although theso-called Overset Mesh (OM) technique can be employed to realize therigid motion of lifeboats in the FV framework, it is well-known that there
exist serious field discontinuities at the overset-background interface thatis devoted to exchanging flow information between these two regions,which could somewhat reduce the accuracy of the FV results.

KEY WORDS: lifeboat launching; smoothed particle hydrodynamics;
finite volume method; water entry dynamics; fluid-structure interaction

In order to resolve the aforementioned issues, another paradigm named
Lagrangian particle-based method can be a more suitable tool for suchproblems. At present, there have been various meshless methods,
including Smoothed Particle Hydrodynamics (SPH) (Monaghan, 2005),
Moving Particles Semi-implicit (MPS) method (Khayyer et al., 2019),
and Generalized Finite Difference Method (GFDM) (Huang et al., 2020),
etc. These methods have been significantly improved for solving realengineering problems in the past decades due to the development of thecomputer industry. For instance, recently Meng et al.(2022) proposed theTENO-SPH scheme that further improves the numerical accuracy of theSPH method in hydrodynamics. Despite the fact that the SPH method is
now being widely applied to extensive industrial problems, such as
coastal and ocean engineering (Gotoh and Khayyer, 2018; Gotoh et al.,2021; Luo et al., 2021), ocean energy devices (Brito et al., 2020; RoperoGiralda et al., 2020; Lyu et al., 2022), manufacturing engineering (Daoand Lou, 2021; Meier et al., 2021), and even biomedical engineering(Zhang et al., 2021), it seems that the problems of lifeboat water entry
have received limited attention in the past years (Shibata et al., 2013;

INTRODUCTION
Water entry problems are one of the most important topics in oceanengineering since such phenomena involve extensive complex physicalprocesses, e.g. hydroelasticity, turbulence, cavitation, multiphase effects,and Fluid-Structure Interaction (FSI) (Truscott et al., 2014). Among thewater entry problems, the lifeboat water entry is tightly related to thesafety of passengers when undergoing serious maritime accidents (vanDam et al., 2014). Therefore, this topic is worth receiving the attentionof the ocean engineering community to offer a better design of lifeboats.
There is no doubt that for such complex FSI processes, experimental
methods can be one of the most reliable strategies to investigate the water
entry dynamics for different objects. Notwithstanding, two limitations
block the wide application of this method in practical applications. One
is that the scaling effect from model tests is inevitably encountered when1983