...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>International Journal of Heat and Fluid Flow >Time Resolved Scanning PIV measurements at fine scales in a turbulent jet
【24h】

Time Resolved Scanning PIV measurements at fine scales in a turbulent jet

机译：湍流射流中细尺度的时间分辨扫描PIV测量

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The temporal and spatial complexity of turbulent flows at intermediate and small scales has prevented the acquisition of full three-dimensional experimental data sets for validating classical turbulent theory and Direct Numerical Simulations (DNS). Experimental techniques like Particle Velocimetry, PIV, allow non-intrusive planar measurements of turbulent flows. The present work applied a Time Resolved Scanning PIV system, TRS-PIV, capable of obtaining three-dimensional two-component velocities to measure the small scales of a turbulent jet. When probing the small scales of these flows with PIV, the uncertainty of the measured turbulent properties are determined by the characteristics of the PIV system and specially the thickness of the laser sheet. A measurement of the particle distribution across the thickness of the laser sheet is proposed as a more detailed description of the PIV sheet thickness. The high temporal and spatial resolution of the TRS-PIV system allowed obtaining quasi-instantaneous volumetric vector fields at the far field of a round turbulent jet in water, albeit for a low Reynolds number of 1478 due to the speed limitations of the present camera and scanning system. Six of the nine components of the velocity gradient tensor were calculated from the velocity measurements. This allowed the visualization with near Kolmogorov-scale resolution of the velocity gradient structures in three-dimensional space. In general, these structures had a complex geometry corresponding to elongated shapes in the form of sheets and tubes. An analysis of the probability density function, pdf, of the velocity gradients calculated showed that the on-diagonal (off-diagonal) velocity gradient components were very similar to each other even for events at the tails of the pdfs, as required for homogeneous isotropy. The root mean square of the components of the velocity gradients is also calculated and their ratio of off-diagonal components to on-diagonal components satisfied the 2 factor required for homogeneous isotropic flows. The ratio of the longitudinal Taylor scale to the transverse Taylor scale was also calculated agreeing with the homogeneous isotropic turbulence requirements within 1%.
机译：中小尺度湍流的时间和空间复杂性阻止了完整的三维实验数据集的采集，以验证经典的湍流理论和直接数值模拟（DNS）。诸如粒子测速，PIV之类的实验技术允许对湍流进行非侵入式平面测量。本工作应用了时间分辨扫描PIV系统TRS-PIV，该系统能够获得三维二维分量速度来测量湍流射流的小尺度。当用PIV探测这些流动的小规模时，测得的湍流特性的不确定性取决于PIV系统的特性，尤其是激光片的厚度。作为对PIV片厚度的更详细的描述，提出了在整个激光片厚度上的颗粒分布的测量。 TRS-PIV系统的高时间和空间分辨率允许在水中圆形湍流射流的远场获得准瞬时体积矢量场，尽管由于本相机的速度限制和低雷诺数1478，扫描系统。根据速度测量结果计算出速度梯度张量的九个分量中的六个。这使得三维空间中的速度梯度结构具有接近Kolmogorov尺度分辨率的可视化效果。通常，这些结构具有复杂的几何形状，对应于片和管形式的细长形状。对所计算出的速度梯度的概率密度函数pdf的分析显示，对角（离对角）速度梯度分量彼此非常相似，即使对于pdf尾部的事件也是如此，这是均匀各向同性所必需的。还计算了速度梯度各分量的均方根，其斜对角分量与斜对角分量之比满足均质各向同性流所需的2个因子。还计算出纵向泰勒标度与横向泰勒标度的比率，以使均质各向同性湍流要求在1％以内。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号