层流圆管潜射流生成蘑菇型涡结构特性实验  

EXPERIMENTS ON EVOLUTION CHARACTERISTICS FOR THE MUSHROOM-LIKE VORTEX STRUCTURE GENERATED BY A SUBMERGED LAMINAR ROUND JET

作　　者：陈科[1] 尤云祥[1] 陈云祥[1] 胡天群[1] 

机构地区：[1]上海交通大学海洋工程国家重点实验室,上海200240

出　　处：《力学学报》2013年第6期843-853,共11页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金(11072153);海洋工程重点实验室基金(GP010819)资助项目~~

摘　　要：利用溢流恒压装置产生具有稳定出流速度的层流圆管潜射流,结合染色液流态显示方法,在多种射流时间和雷诺数组合下,实验研究了该射流动量在密度均匀黏性流体中的演化机理及其表现特征,定量分析了蘑菇型涡结构的无量纲射流长度L、螺旋型涡环半径R及其包络外形长度d等几何特征参数随无量纲时间t的变化规律.系列实验结果表明,蘑菇型涡结构的形成与演化过程可分为3个不同的阶段,分别为启动阶段、发展阶段和衰退阶段.在启动阶段,L和d随t线性变化,而R则近似为一个常数.在发展阶段,蘑菇型涡结构的演化具有自相似性,在各种射流时间和雷诺数组合下,L,R和d与t 1/2均为同一正比关系,而且实验结果与基于斯托克斯(Stokes)近似的理论解结果一致.在衰退阶段,蘑菇型涡结构会发生两类形式的演化,第1类衰退出现在射流结束之后,其间L和R与t 1/5相关,而d近似为一个常数;第2类衰退出现在射流结束之前,当射流动量达到某个临界值后,蘑菇型涡结构就会发生破碎等现象.A constant-pressure spillover system is designed to produce a submerged Laminar round jet with the constant outlet velocity, the flow patterns are visualized by dyed liquid, the evolution mechanism and characteristics due to the jet momentum in viscous uniform fluid is conducted experimentally for different combinations of the injection time and Reynolds number, where three non-dimensional parameters for the mushroom-like vortex structure generated by such a submerged laminar round jet, including the length of the jet L＊, the radius of the mushroom-like vortex R＊ and the length of vortex circulation d＊, are defined and the variation characteristics of these parameters with non-dimensional time t＊ are quantitatively analyzed. Serial experimental results show that the formation and evolution process of such a mushroom- like vortex can be described as three stages： starting, developing and decaying stages. In starting stage, L＊ and d＊ increase linearly with t＊, while R＊ approximately remains a constant. In developing stage, the mushroom-like vortex structure shows a significant self-similarity, where L＊, R＊ and d＊ are approximately proportional to t.1/2 for different combinations of the injection time and Reynolds number, the experimental results agree well with the theoretical solution based on stokes approximation. In decaying stage, two kinds of decay cases will happen for the mushroom-like vortex structure. In the first case, the decay happens after the end of the submerged round jet, where L＊ and R＊ are related to t.1/5, and d＊ approximately remains a constant. In the second case, the decay happens before the end of the submerged round jet, where some broken phenomenon will occur for the mushroom-like vortex structure after the jet momentum reaches the critical value.

关 键 词：圆管潜射流 点动量源 流动显示 蘑菇型涡结构 演化机理 

分 类 号：O352[理学—流体力学]