Numerical study on the near-field characteristics of waves generated by the collapse of a partially immersed axisymmetric granular column into water

Abstract

The near-field characteristics of the wave generated by the collapse of a partially immersed axisymmetric granular column into water is studied numerically using an unresolved computational fluid dynamics and discrete element method coupling framework. The numerical approach is thoroughly validated, ensuring reliable resolution of granular–fluid interactions and wave dynamics. Three distinct wave types are identified: cnoidal-like waves, nonlinear transition waves, and nonlinear oscillatory waves. Two distinct wave-generation mechanisms are proposed to elucidate the transition between different wave types. In addition, the energy evolution during wave generation is analyzed, and the influence of the initial conditions is also examined. Finally, an empirical scaling law for the maximum wave amplitude is proposed. Compared with existing formulas, the present formula incorporates both the granular shape parameter and the water-depth parameter and shows good agreement with the numerical results.