The structure of weakly compressible grid-generated turbulence
The structure of weakly compressible grid-generated turbulence
复制标题
弱可压缩网格生成湍流的结构
DOI：
10.1017/s0022112000003402
复制
发表时间：
2001
影响因子：
3.7
通讯作者：
Y. Andreopoulos
中科院分区：
文献类型：
--
作者：
G. Briassulis;J. Agui;Y. Andreopoulos
在一个大型激波管研究装置中建立了一种衰减的、可压缩的、近均匀和近各向同性的网格生成的湍流。实验使用了空间分辨率为7到26科尔莫戈洛夫粘性长度尺度的仪器。各种产生湍流的网格提供了大范围的湍流尺度，体流马赫数从0.3到0.6，湍流雷诺数高达700。马赫数涨落的衰减规律与描述不可压缩各向同性湍流的衰减规律相似。衰减系数和衰减指数随马赫数的增大而减小，虚原点随马赫数的增大而增大。造成这些影响的一个可能机制似乎是网格的圆柱杆发出的可压缩剪切层的固有增长率很低。首次尝试用12线微型探头测量随时间变化的三维涡量矢量。这也使得可以获得膨胀、可压缩耗散和扩张伸展的估计。结果表明，这些量的波动随流动平均马赫数的增大而增大。与时间相关的涡旋伸展/倾斜矢量和扩张伸展矢量信号表现出较强的间歇性，其特征是高幅度的猝发，其值可达其RMS值的8倍。在暴力程度较低、持续时间较长的事件发生期间。在所有的信号中，有几个这样的爆发很明显，这表明动力流动现象的存在是一个共同的原因。
A decaying compressible nearly homogeneous and nearly isotropic grid-generated turbulent flow has been set up in a large scale shock tube research facility. Experiments have been performed using instrumentation with spatial resolution of the order of 7 to 26 Kolmogorov viscous length scales. A variety of turbulence-generating grids provided a wide range of turbulence scales with bulk flow Mach numbers ranging from 0.3 to 0.6 and turbulent Reynolds numbers up to 700. The decay of Mach number fluctuations was found to follow a power law similar to that describing the decay of incompressible isotropic turbulence. It was also found that the decay coefficient and the decay exponent decrease with increasing Mach number while the virtual origin increases with increasing Mach number. A possible mechanism responsible for these effects appears to be the inherently low growth rate of compressible shear layers emanating from the cylindrical rods of the grid. Measurements of the time-dependent, three dimensional vorticity vectors were attempted for the first time with a 12-wire miniature probe. This also allowed estimates of dilatation, compressible dissipation and dilatational stretching to be obtained. It was found that the fluctuations of these quantities increase with increasing mean Mach number of the flow. The time-dependent signals of enstrophy, vortex stretching/tilting vector and dilatational stretching vector were found to exhibit a rather strong intermittent behaviour which is characterized by high-amplitude bursts with values up to 8 times their r.m.s. within periods of less violent and longer lived events. Several of these bursts are evident in all the signals, suggesting the existence of a dynamical flow phenomenon as a common cause.