15:30 〜 17:00
[AOS13-P04] Using the Discontinuous Bi-viscous model to analyze the three-dimensional flow field and local scour behavior around the Claviaster libycus
キーワード：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.
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.