超声速混合层涡结构内部流体的密度分布特性  

Density distribution characteristics of fluid inside vortex in supersonic mixing layer

作　　者：郭广明 朱林 邢博阳 Guo Guang-Ming;Zhu Lin;Xing Bo-Yang(College of Mechanical Engineering,Yangzhou University,Yangzhou 225127,China;School of Aeronautics and Astronautics,Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]扬州大学机械工程学院,扬州225127 [2]上海交通大学航空航天学院,上海200240

出　　处：《物理学报》2020年第14期120-134,共15页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11802264);江苏省自然科学基金(批准号:BK20180896)资助的课题.

摘　　要：在使用大涡模拟方法获得超声速混合层流场的基础上,利用拉格朗日相干结构法和涡核位置提取方法,得到了涡结构的边界和涡核的位置坐标,并由此提出了涡结构内部流体密度分布的表示方法.通过分析涡结构内部流体的密度在不同情况(如涡结构的空间尺寸、混合层流场的压缩性和涡结构的融合过程)下的变化,揭示出超声速混合层涡结构内部流体的密度分布特性:在弱和中等压缩性的超声速混合层流场中,其涡结构内部流体的密度分布既关于流向(x轴)对称又关于纵向(y轴)对称,涡核处的流体密度最低而涡边界处的流体密度最高,流体密度在连接涡核与涡边界的射线上单调且近似均匀地增加;在强压缩性的超声速混合层流场中,其涡结构内部流体的密度分布不再具有对称性,而且流体密度呈现波动变化的特点;随着涡结构空间尺寸和流场压缩性的增加,涡核处的流体密度降低(最大减少量约为31%-56%),而涡边界的流体密度变化量约为6%-27%;在相邻两个涡结构的融合过程中,涡结构内部流体密度的变化较轻微,表明融合过程很可能是两个涡结构内部流体的对等组合过程.Based on the large eddy simulation,the boundary of a vortex and the coordinates of its core are both obtained by using the Lagrangian coherent structure method and the location extraction method of the vortex core,and thus the method of representing fluid density inside a vortex is proposed.The density distribution characteristics of fluid inside the vortex in a supersonic mixing layer are revealed by analyzing the changes in density of the fluid inside a vortex under different conditions(e.g.spatial size of the vortex,compressibility of the supersonic mixing layer,and merging process of the two paired vortices)as follows.For the weak and medium compressive supersonic mixing layers,the density distribution of the fluid inside a vortex is symmetrical about both the flow direction(x-axis)and longitudinal direction(y-axis),the fluid density at the vortex core is lowest while it is highest at the vortex boundary,and fluid density increases monotonically and nearly uniformly along the ray connecting the vortex core and the vortex boundary.For the strongly compressible supersonic mixing layer,however,the density distribution of the fluid inside the vortex is no longer symmetrical about any flow direction and moreover it shows the fluctuation characteristics of fluid density distribution.With the increase of the spatial size of a vortex and the compressibility of a supersonic mixing layer,the fluid density at the vortex core decreases(the maximum reduction is about 31%–56%)while it changes about 6%–27%at the vortex boundary.In the merging process of two adjacent vortices,the variation of fluid density in the two vortices is slight,which shows that the merging process is probably of a peer-to-peer combination of fluid inside the two adjacent vortices.Considering the practical engineering applications,the density distribution characteristics of fluid inside the vortex in the supersonic mixing layer with different inflow densities of its upper and lower layers are also investigated,and the results show that the density

关 键 词：密度分布 涡结构 超声速混合层 大涡模拟 

分 类 号：O357[理学—流体力学]