The Study Of Damping Absorber For Irregular Waves Based On VOF Method

With development of computer numerical simulation technology, Appling the numerical wave flume to simulate the wave motion, deformation and their interactions with buildings has already become an important development direction of the computational fluid mechanics. In numerical calculation, the infinity of calculate region is impossible. In order to develop the numerical wave flume with absorbing wave-maker, a rational outflow boundary condition is needed and set on the end of the numerical wave flume to absorb reflection wave of the outflow boundary, and infinitely far region is simulated within limited calculation region.In the numerical wave flume based on the Volume of Fluid Method (VOF), to the regular wave, Sommerfeld radiation condition is adopted as open boundary condition in the outflow boundary. To the random wave, because it's composed of many cosine waves of different wave height, period and random initial phase and every wave speed of them is different, so it is difficult to ascertain the wave speed in the outflow boundary, and the Sommerfeld radiation condition is no longer applicable in the irregular numerical wave flume.Based on the Volume of Fluid Method (VOF), the wave damping absorber of the numerical wave flume for irregular waves has been investigated. Setting the Turbulence motion equation and the Renault equation as the governing equations and using the wall function technique in the near-wall region, an absorbing wave-maker is set at the left side of the flume. Then a certain length of the sponge layer for Wave absorption is set in the outflow boundary at the right side of the flume. The absorber effect of different attenuation coefficients of sponge layer is compared and the effect of the reflective of the flume is analyzed for different empirical parameters of the attenuation coefficients. The best attenuation coefficients type of the absorber effect and the scope of the best empirical parameter in the sponge layer for different wave elements are given. According to the dimensional distribution situation of the wave elevation along the flume in the flume, it's seen that using the attenuation coefficients selected of the sponge layer the traveling wave can be absorbed fully in the scope of one or two wave lengths. The computed spectrum agrees well with the target spectrum at different positions of the flume. The numerical results show that the damping absorber technique of the sponge layer adopted in this paper can avoid the reflection generated at the outflow boundary, combined with the wave-making technique the active wave absorption, an irregular wave absorbing numerical wave flume based on the VOF method is realized.