摘要
本文采用直接数值模拟方法,在具有平均标量梯度的各向同性湍流中,研究被动标量的小尺度结构特性及其与湍流场中应变与涡量的关系.对欧拉统计量及拉格朗日统计量的统计表明:标量耗散的形成主要是由于标量梯度同流场的应变张量压缩主轴耦合的结果,而涡量对标量梯度的形成只有较弱的影响,然而它可以间接影响大强度标量耗散的产生.强标量耗散的细微片状结构的形成时间尺度大约为10倍Kolmogrov时间尺度;在形成强标量梯度的细微片状结构过程中,应变强度随标量梯度同步增大,而涡量则先减小后增大,并在5倍Kolmogorov时间尺度时达到最大.
This paper presents a method of direct numerical simulation to study the small-scale structure of passive scalar and how affected by the strain and vorticity in fully developed isotropic turbulence with an imposed constant mean scalar gradient. By computing and analysing the Eulerian and Lagrangian statistics we conclude that： the scalar dissipation is the consequence of scalar gradient preferentially aligning with the compressive strain ;although the vorticity contributes little to the scalar gradient, it has an indirect influence on the forming of intensive scalar dissipation;the sheet-like structure persists for a short period of about 10 Kolmogorov time scale ; during this period, the amplification of strain increases as the scalar gradient increase, and the vorticity first decreases and then increases till reaches its peak at around 5 Kolmogorov time scale.
出处
《工程热物理学报》
EI
CAS
CSCD
北大核心
2007年第6期1056-1058,共3页
Journal of Engineering Thermophysics
基金
国家自然科学(No.50576027)
教育部新世纪创新人才计划资助项目(No.NCET-04-0708)
关键词
均匀各向同性湍流
直接数值模拟
标量耗散率
应变张量
涡量
homogeneous isotropic turbulence
direct numerical simulation
scalar dissipation
strain tensor
vorticity
