高温大气泡与艉流微气泡间聚并作用研究

Coalescence between thermal bubble and warship wake microbubble

舰船利用主机尾气对尾流微气泡进行抑制,其实质是主机尾气生成的高温大气泡对尾流微气泡的聚并作用。本文首先分析主机排放的高温尾气在海水中形成的气泡特点,根据其和海水之间特定的传热及传质过程,在给出两者之间能否聚并的判据后,建立起高温大气泡对尾流微气泡的聚并模型。以此模型为基础,求解相应的聚并系数,进而得出高温大气泡运动状态对聚并作用影响的三个结论:一是Magus与Saffman升力均会显著影响尾流气泡的运动轨迹,并且这一影响随尾流气泡与大气泡间距的减小、尾流气泡尺度的增大而增大;二是大气泡尺度在一定范围内减小时,因受力及惯性等的作用,微气泡聚并的难度降低,聚并系数随之增大;三是随大气泡上浮速度的增加,聚并系数呈先增后减的趋势。本文成果可预测气泡运动参数对聚并速率的影响,对高温尾气大气泡聚并尾流微气泡的过程进行更贴近实际的模拟,为工程应用研究提供理论指导。

Warship wake elimination by using engine exhaust is the essence of gas thermal bubble and wake microbubble coalescence.The paper analyzes the characteristics of gas thermal bubbles from engine exhaust in the seawater.According to the mass and heat transfer of gas and sea,and criterion for bubble coalescence,a model of thermal bubble and wake microbubble coalescence is set up.With the corresponding coalescence coefficient obtained based on the model,three conclusions of thermal bubble movement condition on warship wake suppression are drawn:(1)Magus and Saffman lift force has a remarkable effect on the movement path of wake bubbles,and the influence increases with the decrease of bubble spacing and the increase of wake bubble size;(2)when big bubble size decreases under certain conditions,bubble coalescence gets easier and the coalescence coefficient increases on account of forces and inertia;(3)with the increase of the big bubble velocity,the coalescence coefficient increases first and then descends.The achievement can forecast the impact of the bubble motion parameters on the coalescence rate.Simulation of the big thermal bubble and wave microbubble coalescence which is closer to reality can provide a theoretical guidance for engineering applications.