Study on Turbulent Transport Phenomenon based on Coherent Fine Scale Structure

在本研究中，涡轮传输现象是基于使用直接数值模拟和激光诊断方法的相干精细尺度结构的研究。通过分析DNS数据的同源性、临时和空间地开发的湍流混合层、湍流通道流、旋转同源性湍流和MHD同源性湍流和DNS数据的均匀性。The Mean azimuthal Velocity profile of the fine scale eddies in所有受调查的流量都可以被Burgers' vortex近似。平均直径和最大均匀速度通常在Kolmogorov微尺度上约10次，在r.m.s.上约0.6次。Velocity fluctuation （U-D2 rms）。“相干精细尺度编辑的空间分布与湍流的不同性质密切相关。”在相干精细尺度编辑中心的应变率也是独立于雷诺兹的数量和流动场的，并且可以通过U-D2 rms和Taylor微尺度来缩放。“应变率张量的最大和最小eigen矢量是相对于相干精细尺度eddy和中间eigen矢量的旋转轴的平行旋转轴。”主要应变率的平衡导致了在埃迪平面上旋转的椭圆特征上的平衡，以及在相干精细尺度埃迪面周围较大的能量分配的结果。《椭圆相干精细尺度编辑的证据》是由利用高分辨率数字粒子图像速度测量仪在涡轮混合层中展示的实验。为了研究涡轮传输机制，粒子梯度同源性同位素涡轮，被动标量传输在同源性同位素涡轮和涡轮预混合火焰是有条件的。它展示了连续精细尺度埃迪主导粒子的空间分布、被动标量通量和局部火焰结构在涡轮中的产生和分化。

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.