Rigid block characteristics on subaerial landslide-tsunamis using a 3D coupled Eulerian-Lagrangian model

To quantitatively reveal how rock blocks falling into water affect the impulse waves, the influence of a rigid block on induced first wave and second wave is systematically investigated. The block characteristics include the initial velocity, density, volume, and incident angle, and the investigated wave behavior characteristics include the maximum kinetic energy of the water, the transformation ratio of the kinetic energy from the block to the waves, the duration of the waves, the maximum movement speed, and the maximum height and width of the waves. The coupled Eulerian-Lagrangian method (CEL) is introduced to establish the numerical models of the fluid-solid coupling, and a laboratory test of a rigid wedge sliding into water demonstrates that it can reasonably describe the dynamic behavior of a landslide-induced wave. A typical process of a block entering water and its energy variation are described and analyzed in detail. Further, the relationship between each characteristic parameter of the block and the waves is quantitatively investigated and fitted. The simulation results show that energy exchange between the block and the water is very rapid after the block collides with the water. The maximum kinetic energy, maximum velocity, duration, and side dimension of the waves mainly increase non-linearly with the above characteristic parameters of the block. The transformation ratio of the kinetic energy from the block to the water, the first wave, and the second wave are usually below 60%, 45%, and 30%, respectively. The velocity of the block first decreases and then maintains a constant speed after entering the water. The displacement of the block increases linearly with the initial velocity and density of the block and exponentially increases with the block volume at different times. With the increase in the incident angle of the block, the kinetic energy and scale of the second wave increase correspondingly.