压缩性对涡环物理特征及其传播速度的影响规律

The Compressible Effect on Characteristics and Translate Velocity of Vortex Ring

在3维可压缩流场中,涡环是最基本的涡结构.为了揭示压缩性对涡环物理特征的影响规律,基于有限体积法求解3维可压缩Navier-Stokes方程,研究激波管产生的轴对称可压缩涡环.可压缩涡环的可压缩性由局部马赫数与涡马赫数定量表征;可压缩涡环的形态特征分为3类,分别为亚声速特征、跨声速特征及超声速特征.在可压缩性的作用下,涡环的结构参数受到一定的影响:涡核内涡量的分布愈加偏离高斯分布,表现为涡量集中区域范围愈加狭窄;涡环半径随着可压缩性的增加逐渐增加;涡核半径先增加,在可压缩性更强且存在嵌入激波的情况下又略微有所减小;涡环的传播速度与可压缩性成正比,由涡马赫数计算得到的理论传播速度与计算结果基本一致,表明了传播速度理论公式同时适用于这3种特征的可压缩涡环.

Vortex ring is the fundamental structure in three dimensional fluid field.Three dimensional Navier-Stokes simulations are performed through finite volume method to reveal the compressible effect on axial symmetry vortex ring generated at the open end of a shock tube.Local Mach number and vortex Mach number can characterize the compressibility quantificationally.Compressibility vortex ring can be classified into three categories which correspond to subsonic,transonic and supersonic.The parameters related to vortex ring structure are also affected by compressibility.As the increase of compressibility,the vorticity profile in vortex core deviates from Gaussian distribution and the concentrated vorticity fields in the vortex core diminishes;the radius of vortex ring increase with the increasing compressibility;the radius of vortex core increase first then decrease slightly due to the embedded shock wave.The velocity of vortex ring is proportional to the compressibility.The theoretical velocity obtained from simulation agrees well with the calculated value obtained by vortex Mach number,which indicates that the formula is suitable to all three kinds of compressible vortex rings.