Dynamic response of submarine obstacles to two-phase landslide and tsunami impact on reservoirs

Submarine landslides may generate super-tsunamis as they interact with water bodies such as oceans, mountain lakes or reservoirs. These water bodies may contain solid objects (obstacles), which substantially alter the mass flow dynamics and reduce the devastating effects of submarine landslide and tsunami. Submarine landslides, the related tsunamis, and their interactions with obstacles are more complex than subaerial landslides and their obstacle-interactions. In order to mitigate mountain and coastal hazards and maintain the integrity of a hydraulic reservoir, it is important to properly understand submarine landslide and tsunami interactions with obstacles. Existing approaches cannot take into account other important aspects of interfacial momentum transfer in mixture flows such as interfacial drag, buoyancy, mobility of the fluid at the particle surface, and virtual mass force, which play important roles in the more accurate prediction of mixture flow dynamics by dynamic interactions between the landslide mass and the water. In order to include these important physics of two-phase mass flows and especially to include dynamic interactions between the landslide mass and the water, we apply a general two-phase mass flow model (Pudasaini in J Geophysics Res 117:F03010, 2012. https://doi.org/10.1029/2011JF002186 ) and present high-resolution novel simulation results for a two-phase landslide impacting a fluid reservoir. Our simulations demonstrate that the intense flow-obstacle-interaction dramatically reduces the flow momentum resulting in the rapid energy dissipation around the obstacles. With the increase in obstacle height, overtopping decreases, but the deflection and capturing (holding) of solid mass increases. Due to multiple obstacles, the moving mass decreases both in amount and speed showing fingering and meandering multiple streamed lobes. The varying location of the obstacles changes the deflection pattern, holding of mass, and tsunami intensity and mobility. Our simulations and findings enrich our understanding of mixing and separation between phases, generation and propagation of special solid and fluid structures, and transitions during the flow process, that may form a basis for the hazard mitigation in coastal regions.