不同盐度下海水表面张力系数的表征研究

摘要

To study the seawater surface tension coefficient representation with different salinities and to simplify the test methods, a practical model for the bubble departure volume and the departure instantaneous velocity is built by analyzing the forces experienced by the bubble in the seawater.The underwater gas emission experimental platform is constructed.It uses the normal pressure air and six kinds of salinity seawater as the experiment's gaseous phase and liquid phase.And the bubble motions are categorized as slow motion with low Reynolds number and fast motion with high Reynolds number.Experiments with both bubble motions are conducted.The high-speed photography technology is used to record the bubble motion, and the filmed pictures are analyzed by the MATLAB program, so as to obtain the bubble departure volume and the departure instantaneous velocity.Substituting the experimental data into models, the seawater surface tension coefficient representation with different salinities can be acquired.The result shows that, under the non jet generation and flotation condition, the bubble is of small radius and has slow movement with low Reynolds number.The simulation results are in consistency with the measurement with high credibility and low divergence.The error is less than 2%.%为研究不同盐度下海水表面张力系数的表征,并精简其表面张力系数的测定手段,根据气泡在海水中的受力情况,建立了海水中的气泡脱离体积及瞬时稳态上浮速度模型.通过搭建气体水下排放试验台,使用常压空气和6种不同盐度的海水分别作为实验的气相和液相,将气泡划分为低雷诺数缓慢上浮及高雷诺数快速上浮2种运动状态,并分别进行实验.用高速摄影技术对气泡运动进行实验观测,通过MATLAB编程对拍摄的图像进行分析处理,测定气泡脱离体积及瞬时稳态上浮速度.将实验数据代入到所建立的模型中,获得不同盐度下海水表面张力系数表征函数.结果表示,当气泡在非射流情况下生成及上浮时,气泡处于小半径慢速运动状态,属于低雷诺数运动过程,海水盐度与表面张力系数拟合效果理想,模型计算值与实验数据符合良好,偏离程度不到2%.