An experimental study on the motion of solid spheres under solitary wave attack

Abstract

In the present study, the motion of a single and the motion and collision of two spheres on a horizontal area under solitary wave attack are investigated, constituting a unique and integrated dataset. Sixteen experimental cases are considered on four experimental configurations changing the number of spheres, the porosity of the bottom, water levels, and the breaking condition of the solitary waves (non-breaking or breaking). The motion of the spheres is tracked using a color-detection-based image-processing algorithm. The experiments reveal four significant results: (i) The rate of damping on the porous bottom is 1.65 times of impermeable bottom on average. (ii) The water level changes the characteristics of the motion of the spheres significantly due to the friction forces and vortex structures created by the interaction of waves with moving spheres. (iii) The dimensionless terminal velocities of the spheres in the non-breaking cases are 1.38 times of breaking solitary wave cases on average. (iv) The type of solitary wave and the water level significantly affect the collision behavior; however, the bottom condition does not have an apparent contribution to the collision behavior.