Experimental Study on Nonlinearity Characteristics Near the Free Surface in the Regular Wave Condition

J. Ocean Eng. Technol. 2010;24(1):1-9.

Choi Hae-Jin,Jung Kwang-Hyo,Suh Sung-Bu,Jo Hyo-Jae,Choi Han-Suk

Hanjin Heavy Industries & Construction Co. Ltd.,Department of Naval Architecture and Ocean Engineering Dong-Eui University,Department of Naval Architecture and Ocean Engineering Dong-Eui University,Division of Naval Architecture and Ocean Systems Engine

Keywords: Regular wave, Particle image velocimetry technique, Water velocity, Local acceleration, Convective acceleration, Nonlinearity

Abstract

A series of experiments employing particle image velocimetry (PIV) technique was conducted to produce benchmark wave kinematics data for regular waves having four different wave slopes in 2-D wave tank. Water velocities and accelerations near the free surface of regular waves were computed from image pair obtained by PIV systems. With the measured wave velocity field, the wave accelerations were computed using a centered finite difference scheme. Both local and convective components of the total accelerations are obtained from experimental data. With increasing the wave slope, the horizontal velocity and the vertical accelerations near the wave crest obtained by PIV technique became larger than theoretical results, which are well-known phenomena of the wave nonlinearity. It is noted that the relative magnitude of convective acceleration to the local acceleration became larger with increasing wave slope.