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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

Research on the Hydrodynamic Influence Factors of Underwater Vehicle in Internal Wave
Miaomiao Huang, Jilong Chu, Mo Chen, Aijun Zhu, Nan Zhang
China ship scientific research center
Wuxi City, JiangSu Province, China

ABSTRACT

may be 2m/s or higher. Therefore, the destructive forces of internalwaves are very strong. Nonlinear solitary waves especially with large
amplitude are serious threats against the security of ocean engineering
structures (Li, 2015).
The generation, propagation and evolution of nonlinear internal waves
are understood on the basis of various mathematical models andequations, such as the KdV equation, Benjamin-Ono equation andBoussninesq equations. After years of research, internal wave
simulated in stratified fluid tank is relatively easy to achieve inlaboratory as well as in numerical tank. Internal solitary waves
represent the coexistence of nonlinearity and dispersion. In numericalsimulation, internal solitary waves are generally described by KdVequation. KdV theory was first proposed by D. J. Korteweg and G. deVries (Korteweg, 1895). In recent years, interactions of large-amplitudeinternal waves with objects attracted many scholars. There are muchworks done on internal waves generated by submerged body instratified fluid. Many experiments and calculations have been carriedout to study the characteristics of internal wave wake (Meunier, 2018,Li, 2002, Mei, 1991). In contrast, there are relatively few studies on theimpacts of ocean internal waves (naturally existing) on submarine.
Computations of viscous turbulence flow around constrained submarine
has been widely adopted to study the hydrodynamic loads exerted byISWs. Some hydrodynamic properties of bodies in internal waves havebeen revealed (Guan, 2012; Shen, 2016; Xu, 2021). And experiments
were also carried out by using constraint models in stratified fluid tank(Du, Wei, et al., 2016). These research work forms the basis of furtherresearch. This paper focuses on the hydrodynamic influencing factorsof underwater vehicle in internal wave. So a comparative research on
the hydrodynamics of underwater vehicles in different conditions wascarried out by numerical simulated method.

In this paper, the hydrodynamic force and flow fields of underwater
vehicle encountering internal solitary wave (ISW) were simulated bynumerical method. KdV internal solitary theory was used to modelingthe induced currents. Firstly, we focused on general hydrodynamic
characteristics. Simulated results show that under the action of internalwave, the unsteady variation rule of hydrodynamic forces is obvious.
Secondly, internal wave amplitude, speed and submergence depth weretaken into research respectively. The results in this paper are
meaningful to influence research of underwater vehicles in internal
waves.

KEY WORDS: hydrodynamic; numerical simulation; internal
solitary wave; influence.
INTRODUCTION
In the density stable stratified ocean, when the seawater tide flows
through the dramatically changing terrain such as submarine ridge, theinternal wave will be excited at the ridge (Fang, 2005). The internal
wave is a common marine phenomenon in ocean, especially in themarginal sea. Figure 1 (Jackson, 2004) demonstrates the widespreadoccurrences of internal waves around the world compiled in the Atlasof Oceanic Internal Solitary Waves.

METHODOLOGY
Water is assumed to be incompressible and isothermal Newtonianfluids. Flows are three dimensional, turbulent. The continuity equation
and Reynolds time averaged N-S equations (RANS) can be written inCartesian tensor notation as follows:__ ui0xi

Fig.1 Locations of internal waves around the world
Large amplitude internal solitary wave can cause strong convergenceand divergence of seawater which are like sudden strong currents (Fang,2005). The maximum velocity of flow fields induced by internal wave2403__u(1)__ __u____ p__u ti   u j x i   Fi  x  x (  x i  ji
jj_______ui'u 'j )(2)