Japan Geoscience Union Meeting 2023

Presentation information

[E] Online Poster

A (Atmospheric and Hydrospheric Sciences ) » A-OS Ocean Sciences & Ocean Environment

[A-OS13] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

Wed. May 24, 2023 3:30 PM - 5:00 PM Online Poster Zoom Room (1) (Online Poster)

convener:Shin-ichi Ito(Atmosphere and Ocean Research Institute, The University of Tokyo), Takafumi Hirata(Arctic Research Center, Hokkaido University), Eileen E Hofmann(Old Dominion University), Jessica A. Bolin(University of the Sunshine Coast)


On-site poster schedule(2023/5/24 17:15-18:45)

3:30 PM - 5:00 PM

[AOS13-P04] Using the Discontinuous Bi-viscous model to analyze the three-dimensional flow field and local scour behavior around the Claviaster libycus

*PIN JIE LIN1, Tso-Ren Wu1, Jih-Pai Lin2, Thi-Hong-Nhi Vuong3, Yi Xuan Huang1, Zih-Syuan Fan1, JIA-JIE CHI4 (1.Graduate Institute of Hydrological and Oceanic Sciences, National Central University, Taiwan, 2.Department of Geosciences, National Taiwan University, Taiwan, 3.lecturer in the Department of Aerospace Engineering at the Ho Chi Minh City University of Technology, Vietnam, 4.Department of Earth Sciences, National Central University, Taiwan)


Keywords:Splash3D, Discontinuous Bi-viscous Model DBM, Local scour, Claviaster libycus

According to previous studies, the survival rate of Claviaster libycus after mass extinction is higher than that of regular echinoids. This study aims to analyze the flow field and scour behavior induced by the unique distorted shape of Claviaster libycus through numerical modeling and explores the possibility of applying this mechanism to reduce the local scour induced by the foundation of hydraulic structures.

The numerical model, Splash3D, used in this study is modified from the open-source code, Truchas, developed by the National Laboratory of the United States. Splash3D solves the three-dimensional incompressible Navier-Stokes equations. Water surface kinematics and sand surface kinematics are described by the Volume of Fluid Method (VOF).

Since Claviaster libycus semi-submerges in the sand, the discontinuous bi-viscous model (DBM) is used to describe the rheological behavior of bottom sand. DBM is developed based on the conventional Bingham Model (BM). In contrast to the BM model, the DBM model uses the yield strain rate instead of yield stress to distinguish the plug from the liquefied zone. In the Plug zone, a high viscosity represents solid characteristics. The plug-zone viscosity is much higher than the liquified zone's. Liquified zones indicate sand disturbed by local currents around irregular echinoids, while plug zones represent sand undisturbed by the flow. The yield strain rate determines the stiffness of the bottom sand. Local scour around obstacles is described by the DBM model.

Based on three-dimensional numerical simulations, Claviaster libycus can reduce the generation of horseshoe vortexes and further reduce local scour around sea urchins. Detailed analysis results are presented in the full text.