【摘要】 利用流动显示技术,观察并分析了内射流出口处形状改变(大矩形、小矩形、正方形、大椭圆、小椭圆、圆形)时,以及射流出口处形成平面对称剪切流时,涡流的生成、发展、配对、归并以及破裂的空间演化行为.实验发现:以上两个实验背景下均存在环涡结构及螺旋涡结构.环涡的归并存在"偶极子"和"三极子"现象.环涡结构在速度的诱导下发生偏转,并且在一定的雷诺数临界值后形成了螺旋涡结构,此雷诺数临界值与射流出口处的形状有关.螺旋涡在雷诺数的变化下有不同的结构;其旋转方向随着速度比的变化存在左旋、右旋现象;同时其螺距随着速度比的增加而增大.更多还原

【Abstract】 Some spatial evolution actions(rolling up,growing up,pairing,merging and breaking up)of vortices have been observed and analyzed,by making use of the flow visualization,when the boundary of the outlets of jet inflows is changed to different shapes(big rectangular,small rectangular,square,big elliptic,small elliptic and circular)or the planar-symmetric shear flows is produced at the outlets of jet flows.Toroidal vortices and helical vortices both exist in the two experiments above.The pairing of toroidal vortices has the"Batchelors couples"or"tri-poles"phenomena.Results show that,behind a certain critical value of Reynolds number which is determined by the shape of outlets,toroidal vortices turn to helical vortices because of their deflecting during the change of the speed.It is also shown that helical vortices have different structures during the change of Reynolds number;their direction of rotation has the left-hand and right-hand phenomena due to the velocity ratio;their screw pitch is in direct proportion to the velocity ratio.更多还原