In general, the numerical simulation of harbor tranquility always treats the reflection coefficients of solid boundaries as constant for all wave periods, which is differ from real situation that the reflection coefficients of a solid boundary are varied by the wave period. In this study, such difference was investigated. Mallayachari and Sundar's (1994) results of wave absorption characteristics of porous media were employed on the solid boundaries during the simulations. The results show that the changes of reflection coefficient to wave period should not be ignored in numerical simulation. The modified model of harbor tranquility is more suitable in practice, and is more applicable in harbor planning and design.
The tranquility inside a harbor plays the major concern when designing and planning a harbor. Many researchers in the past and now devote plenty of time on studying this problem, by using theoretical, numerical or experimental method to investigate the wave-induced oscillation inside a harbor. To economize on time during the planning and designing, numerical approach seems to be more efficient than hydraulic model experiment. Therefore, various numerical schemes were developed to analyze wave refraction, diffraction, reflection and dissipation problems. For example, Mile & Munk (1961) considered wave energy radiation effect expanding from harbor entrance to offshore and applied Green function to analyze harbor oscillation. It is also found the phenomenon of harbor paradox. Ippen & Goda (1963) applied Fourier transformation method to solve the harbor resonance of rectangular harbor and obtained the solution by matching the wave amplitude and velocity approximately at entrance. Lee (1969) discovered the trapping of energy by the harbor that lead to the amplitude of oscillation far greater than incident wave amplitude. Hwang & Tuck (1970) used a boundary integral method to calculate oscillation in harbors of constant depth with arbitrary shape.