[M-IS07] 地球表層における粒子重力流のダイナミクス

[MIS07-02] Self-stratifying turbidity currents

*Edward Skevington¹、Robert Dorrell¹ (1.Univ. of Hull)

キーワード：Turbidity current, Long run out, Levee overspill, Energetics, Depth averaged

We develop a new, channel-averaged model for turbidity currents that captures the evolving vertical structure as the current moves along the channel. This changes how the system scale energy conservation is imposed, showing that the production of turbulent energy is larger than previously believed. In addition, the inclusion of an evolving vertical structure changes the appropriate Froude number and classification of criticality, which can be interpreted as a condition on the energetics of the flow. Both the changes in energy production and criticality condition show that principles from classical hydraulics may have severe shortcomings when applied to turbidity currents. The model also includes levee overspill, derived with consideration of the imposed vertical structure. This acts to enhance the depth average particle concentration, momentum, and energy, because the fluid at the top of the channel that undergoes overspill has below average concentration of all three. The enhancement aids in maintaining supercritical flow (in the updated sense) until the end of the channel-levee system. We apply our model to a physical system, the Congo canyon-levee system, demonstrating that our model captures the essential physics necessary to predict the long run-out seen in nature.