Experimental study of plunging solitary waves impacting a vertical slender cylinder

Solitary waves can evolve into breakers in the nearshore area, generating strong destructive forces, especially for plunging breakers. In the present study, experiments are conducted to investigate plunging solitary waves propagating over a trapezoidal bar and to quantify their subsequent hydrodynamic forces on a cylinder. To do so, solitary waves are designed to break at varying phases and to strike the cylinder differently in space to examine their hydrodynamic forces. Furthermore, consideration of structural responses influencing measured forces for non-rigid structures provides the basis of an equation of motion that facilitates the extraction of hydrodynamic forces from measured forces. Additionally, the relation of cylinder's properties to surface elevations are evaluated and subsequently used to extract the hydrodynamic forces. The results show that the measured forces, extracted hydrodynamic forces, and dynamic amplification factors (DAF: ratio between the measured force and hydrodynamic force) achieve their highest values approximately at the same breaking phase, that is when the plunging jet has curled down, but prior to its impingement on the water surface, and this remains valid for different incident wave heights. Lastly, with an assumed asymmetrical triangular-pulse force, theoretical DAF is calculated and presents less than a 20% difference to the experimental DAF.