有障碍圆形浮力射流的绕流流态研究

针对静止环境中有障碍圆形浮力射流出现的正常绕流现象与非正常绕流现象（反射与分叉现象），分析了其主要的3个影响因素:障碍盘直径D/d（D和d分别是障碍盘和射流出口的直径），射流出口密度Froude数以及障碍盘离射流孔口的距离H/d与发生非正常绕流之间的相互关系．得到了H/d=2,4,6,8在不同D/d值时发生非正常绕流的临界密度Froude数．对直径为D/d的障碍盘，当其离射流孔口的距离H/d达到某一值时，流动仅为正常绕流流态．基于大量计算给出了不同障碍盘所要求的H/d值，综合以上因素得到了临界密度Froude数的拟合公式．对非正常绕流中射流出现反射与分叉的规律性进行了探讨．对D/d=1的有障碍浮力射流进行的数值计算表明，所有工况下的流态均为正常绕流，并得到了不同H/D条件下的轴线稀释度．

Research on Rounded Flowing States of Obstructed Buoyant Jet

The mutual relationships of three effective factors,the diameter D/d (d is the diameter of exit) of obstructed plate,exit densimetric Froude number and the distance H/d of the plate from jet orifice for obstructed buoyant jet in static ambient,were analyzed to explain normal and abnormal rounded flowing (reverberated and bifurcated flowing).The critical Froude numbers for obstructed buoyant jets with H/d=2,4,6,8 which distinguished normal and abnormal flowing pattern were obtained.Normal rounded flowing is found only for a plate under a special value of H/d.A fitted formula of critical Froude numbers with H/d and D/d was presented to distinguish rounded flowing types.The occurring of reverberated or bifurcated flowing in abnormal rounded flow was analyzed.Based on the results of obstructed buoyant jets with D/d=1,normal rounded flowing occurred only for all conditions and axial dilution behind the plate under different H/D is obtained.