圆射流中拟序涡配对的数值模拟

Numerical Simulations of Coherent Vortex Pairing in a Round Jet

用三维涡丝法结合涡丝的增加与合并技术,对不可压圆射流场,数值模拟了在扰动中加入次谐波后流场拟序涡的配对,配对情况与实验结果一致,通过对不同时刻涡量图的比较与分析,给出了次谐波初始强度对涡配对的影响,初始强度越大,涡配对出现越早,涡配对位置越往上游移动;同时还得到了基波与次谐波初始相位差和涡配对的关系,没有相位差时,次谐波增长最快,相位差增加时,涡配对的速度降低。说明控制次谐波的初始强度和基波与次谐波的相位差,能起到控制圆射流剪切层乃至控制整个射流场的目的。

The three-dimensional vortex filament method combined with the addition and amalgamation techniques for vortices was employed to simulate an incompressible round jet. The process of coherent vortex pairing under the subharmonic perturbation was obtained, which is in good agreement with the experimental results. The effects of the initial intensity of the subharmonic perturbation and initial phase difference between the fundamental perturbation and the subharmonic one on vortex paring was investigated by comparing and analyzing the figures of vorticity at different times. The larger the initial intensity of the subharmonic perturbation is, the earlier vortex pairing appears. The subharmonic perturbation increases in the most fast when there is no phase difference. While phase difference increases, vortices pair slowly. The results show that the shear layer as well as round jet can be controlled by changing initial intensity of the subharmonnic perturbation and initial phase difference.