船舶尾流散射光信号及一维离散小波分析

用自行设计的测试系统测量了不同航速下船舶尾流的散射光信号,并选用一维离散小波Dmeyer小波对散射光信号进行了5层小波分析.测量和分析结果表明,随着航速增大,船舶尾流散射光照度减小,尾流气泡幕逐渐增强,气泡幕中气泡密度、气泡运动规律、不同直径气泡分布均随之变化.气泡幕的增强可能存在饱和度,在航速增大到一定值时,气泡幕会达到一稳定的密度分布.从小波分析得到的第五层逼近信号来看,不同航速下主峰位置、主峰个数以及峰值差均不同,不同航速下散射光细节信号的第一层均具有一定周期性,航速10 km/h时表现出完美的周期性,出现类似于同方向不同频率简谐振动叠加而出现“拍”的现象.

Scattered Light Signal of Ship Wakes and One-dimension Disperse Wavelet Analysis

The scattered light signal is measured by use of designed experimental system.Five levels wavelet transformation are carried out choosing one-dimension disperse Dmayer wavelet.Ship wakes′ scattering illumination abates with speed accretion of the ship,according to the analytic results, and bubble density,motion,diameter distribution will change with that. Saturation can be reached possibly and steady density distribution can be got with the ship speed increasing.The situation, number, and value of peaks are different each other on fifth level approach gained from wavelet transformation which presents that the first level detail of scattered signal vibrates in periodicity.The perfect periodicity under a speed of 10 km/h is similar to the superposition of two simple harmonic oscillations that gives an appearance of beats.