舰船远场尾流气泡分布特性的数值模拟

Numerical Simulation of Bubble Distribution Characters in Ship′s Far Field Wakes

为了了解舰船尾流中气泡的分布特征,为激光探测舰船尾流提供依据,建立了计算热分层环境中舰船远场尾流中气泡数密度分布的数学模型,该模型由抛物化的RaNS方程及气泡输运方程组成,采用k-ε两方程湍流模式.利用该模型数值模拟了舰船尾流中的气泡数密度分布特征、气泡尾流宽度扩展规律,气泡数密度衰减规律,并与实测结果进行了比较,二者定性符合得较好.数值模拟表明舰船尾流中半径为10 ～30μm的气泡存活时间最长,为了确保能在距船尾5 km处还能探测到舰船气泡尾流,其探测的对象应以半径10 ～30μm的气泡为主,并且探测准确度至少应能达到识别出初始截面上气泡数密度的3 %.

The mathematics model, which can calculate bubble number density distribution in ship＇s far field wakes in the thermal stratified ocean environment is established for understanding the bubble distribution characters in ship wakes and providing the basis of detecting ship wakes. The model is made of parabolic Reynolds-averaged Navier-Stokes equations （PRaNS） and bubble transport equation in which the well known k-εmodei is used. The characteristics of bubble number density distribution in ship wakes, the spread law of the bubble wakes width and the attenuation law of bubble number density are calculated usingthe model. The calculation results are compared with the measuring results of ship wakes,they agree well with each other qualitatively. The numerical simulation results show the bubbles which radius being 10- 30 microns exist the most long time in the wakes. The detected object should be focused on the bubbles which radius being 10-30 microns for detecting the ship bubble wakes from the ship＇s stern 5 kilometers at least, and the precision of detection should reach the level which can distinguish the 3% bubble number density at initial plane.