17:15 〜 19:15
[SCG50-P04] Coupled Dynamics of Internal Waves and Submarine Landslides in the Formation of Nepheloid Layers
キーワード：Nepheloid, VOF, Concentration Gradient method, Internal waves, Seabed sediment, Submarine landslide
The nepheloid layer is a turbid oceanic layer characterized by a high concentration of suspended particles, widely distributed across global oceans and their margins. Based on its distribution and formation mechanisms, nepheloid layers can be categorized into three types: the Surface Nepheloid Layer (SNL), Intermediate Nepheloid Layer (INL), and Bottom Nepheloid Layer (BNL). The SNL primarily originates from biological activity and riverine inputs, while the INL is associated with the propagation and reflection of internal waves, such as internal solitary waves. The BNL results from the resuspension of bottom sediments due to strong water currents or seabed storms.
Internal waves interacting with continental slopes or submarine canyons can generate localized vortices that mobilize seafloor sediments, contributing to nepheloid layer formation. Meanwhile, submarine landslides are complex transport processes that involve sediments of varying grain sizes. Fine particles contribute to turbidity currents, while coarse sediments form debris flows. In turbidity currents, finer sediments remain suspended due to their slow settling velocity, creating a diffusive suspension effect. This study hypothesizes that the interaction between submarine landslides and internal wave-induced disturbances plays a critical role in nepheloid layer formation. This mechanism complements existing theories, providing new insights into submarine geology and sediment transport.
To investigate these processes, this study employs Splash3D, an open-source computational fluid dynamics (CFD) software based on Truchas, developed by the Los Alamos National Laboratory (LANL). Splash3D solves the Navier-Stokes equations using the Volume of Fluid (VOF) method to discretize velocity and pressure fields within the computational domain.
To enhance the accuracy of submarine landslide simulations, this study introduces the Concentration Gradient Method (CGM), which improves the representation of landslide dynamics. Numerical simulations incorporating the interaction between internal waves and submarine landslides were conducted to quantify nepheloid layer formation. The results indicate that under conditions of seawater density stratification, suspended sediments from submarine landslides can oscillate at density interfaces, leading to the formation of nepheloid layers along these boundaries. Furthermore, the intensity of these layers increases with greater density contrast. Beyond the influence of density stratification, this study also examines the effects of varying submarine landslide material densities and sediment transport behavior under different collapse scenarios. These findings contribute to a deeper understanding of nepheloid layer formation and sediment transport dynamics in marine environments.
Internal waves interacting with continental slopes or submarine canyons can generate localized vortices that mobilize seafloor sediments, contributing to nepheloid layer formation. Meanwhile, submarine landslides are complex transport processes that involve sediments of varying grain sizes. Fine particles contribute to turbidity currents, while coarse sediments form debris flows. In turbidity currents, finer sediments remain suspended due to their slow settling velocity, creating a diffusive suspension effect. This study hypothesizes that the interaction between submarine landslides and internal wave-induced disturbances plays a critical role in nepheloid layer formation. This mechanism complements existing theories, providing new insights into submarine geology and sediment transport.
To investigate these processes, this study employs Splash3D, an open-source computational fluid dynamics (CFD) software based on Truchas, developed by the Los Alamos National Laboratory (LANL). Splash3D solves the Navier-Stokes equations using the Volume of Fluid (VOF) method to discretize velocity and pressure fields within the computational domain.
To enhance the accuracy of submarine landslide simulations, this study introduces the Concentration Gradient Method (CGM), which improves the representation of landslide dynamics. Numerical simulations incorporating the interaction between internal waves and submarine landslides were conducted to quantify nepheloid layer formation. The results indicate that under conditions of seawater density stratification, suspended sediments from submarine landslides can oscillate at density interfaces, leading to the formation of nepheloid layers along these boundaries. Furthermore, the intensity of these layers increases with greater density contrast. Beyond the influence of density stratification, this study also examines the effects of varying submarine landslide material densities and sediment transport behavior under different collapse scenarios. These findings contribute to a deeper understanding of nepheloid layer formation and sediment transport dynamics in marine environments.