Cylinder water entry on a perturbed water surface

The perturbations existing on a breaking wavefront can be potential explanation for the slamming pressure variability in wave impacts. Here, we investigate effect of these by forced vertical two-dimensional circular cylinder with constant downward velocity standing waves. Through experimental modelling and numerical simulation, force is measured several amplitudes wavelengths. phase tuned such that impact occurs symmetrically at instant maximum crest or trough. Our observations show coefficients vary amplitude when wavelength kept vice versa. trough coefficient more than two times flat impact, up to four impact. results are reproduced simulations they agree reasonably well general. Two analytical approaches based von Kármán ( NACA , vol. 321, 1929, pp. 1–8) Wagner Z. Angew. Math. Mech. 12, 1932, 913–215) methods, which consider water surface curvature, introduced. calculated from methods provide bound found each wavelength. Further insight achieved shorter diameter ratio $0.05<\lambda /D<0.4$ . As becomes smaller, impacts locations. result, multiple peaks occur, trapped air different locations between yields oscillations frequencies time history.