Study on Turbulent Transport Phenomenon based on Coherent Fine Scale Structure

基于相干细尺度结构的湍流输运现象研究

基本信息

批准号：
09450088
负责人：
MIYAUCHI Toshio
金额：
$ 4.99万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

In this study, turbulent transport phenomenon is investigated based on the coherent fine scale structure in turbulence using direct numerical simulation and laser diagnostics. The universality of fine scale motions in turbulenceis clarified by analyzing DNS data of homogeneous isotropic turbulence, temporally and spatially developing turbulent mixing layer, turbulent channel flows, rotating homogeneous turbulence and MHD homogeneous turbulence. The mean azimuthal velocity profile of the fine scale eddies in all investigated flows can be approximated by the Burgers' vortex. Mean diameter and maximum azimuthal velocity is always about 10 times Kolmogorov microscale and about 0.6 times of r.m.s. velocity fluctuation (UィイD2rmsィエD2). The spatial distribution of the coherent fine scale eddies is closely related with the anisotropy of turbulence. The strain rate at the center of the coherent fine scale eddies is also independent on the Reynolds number and flow fields and can be scaled by UィイD2rmsィエD2 and the Taylor microscale. The maximum and minimum eigen vectors of the strain rate tensor are perpendicular to the rotating axis of the coherent fine scale eddy and intermediate eigen vector is parallel to the rotating axis. The balance of the principal strain rates leads to the elliptic feature on the rotating plane of the eddy, which results in the large energy dissipation around the coherent fine scale eddies. The evidence of the elliptic coherent fine scale eddies was shown by the experiments in turbulent mixing layer using high-resolution digital particle image velocimetry. To investigate turbulent transport mechanism, DNS of particle laden homogeneous isotropic turbulence, passive scalar transport in homogeneous isotropic turbulence and turbulent premixed flames were conducted. It was shown that the coherent fine scale eddy dominates spatial distribution of particles, the generation and dissipation of passive scalar fluctuation and local flame structure in turbulence.

在这项研究中，利用直接数值模拟和激光诊断，基于湍流中的相干精细尺度结构来研究湍流输运现象，通过分析均匀各向同性湍流、时空发展的湍流混合的 DNS 数据，阐明了湍流中精细尺度运动的普遍性。层、湍流通道流、旋转均匀湍流和 MHD 均匀湍流细尺度的平均方位角速度剖面。所有研究的流动中的涡流都可以用伯格斯涡来近似，平均直径和最大方位角速度始终约为科尔莫哥洛夫微尺度的10倍，约为r.m.s.速度波动的0.6倍。相干细尺度涡流的空间分布是紧密的。与湍流的各向异性相关。相干细尺度涡流中心的应变率也与雷诺数和流场可以通过 UiID2rmsIeD2 和泰勒微尺度进行缩放。应变率张量的最大和最小特征向量垂直于相干细尺度涡旋的旋转轴，中间特征向量平行于旋转轴。主应变率的平衡导致涡旋旋转平面呈现椭圆形特征，从而导致相干细尺度涡旋周围存在大量能量耗散。使用高分辨率数字粒子图像测速技术在湍流混合层中进行的实验显示了椭圆相干细尺度涡流的证据，以研究湍流输运机制、载有粒子的均匀各向同性湍流的 DNS、均匀各向同性湍流中的被动标量输运和预混合湍流。结果表明，相干细尺度涡旋主导着粒子的空间分布、粒子的产生和消散。湍流中的被动标量波动和局部火焰结构。