Color-coded visualization of microbubble clouds interacting with eddies in a spatially developing turbulent boundary layer
Color-coded visualization of microbubble clouds interacting with eddies in a spatially developing turbulent boundary layer
复制标题
DOI：
10.1016/j.expthermflusci.2019.109919
复制
发表时间：
2019-12
影响因子：
3.2
通讯作者：
H. Park;Daichi Saito;Y. Tasaka;Y. Murai
中科院分区：
文献类型：
--
作者：
H. Park;Daichi Saito;Y. Tasaka;Y. Murai
实验研究了沿平板发展的湍流边界层中分散的微气泡的三维分布。研究的目的是直观地找出微气泡如何与湍流涡相作用来实现壁面上的摩擦减阻。实验设置条件为流动雷诺数为2.3 × 10 4，边界层内微气泡体积分数小于10−5，微气泡斯托克斯数小于10−3。三维微泡分布通过颜色编码的体积照明可视化。结果表明，微气泡云优先向粘性亚层附近的低速条纹和缓冲层内的发卡涡聚集，导致微气泡的扩散率相对于湍流动量扩散率降低。
Three-dimensional distribution of microbubbles dispersed in a turbulent boundary layer spatially developing along a flat plate is investigated experimentally. The aim of study is to find out visually how microbubbles interact with turbulent eddies to achieve frictional drag reduction on a wall. Setting conditions of the experiments are stream Reynolds number up to 2.3 × 104, microbubble volume fraction inside boundary layer less than 10−5, and microbubble Stokes number smaller than 10−3. Stream-wise vortices in the boundary layer were visualized by flake optics, of which spacing expands with injection of microbubbles. 3-D microbubble distributions were visualized by a color-coded volumetric illumination. The result showed preferentially accumulated microbubble clouds to low-speed streaks close to viscous sublayer and to hair-pin vortices in the buffer layer, leading to reduced diffusivity of microbubbles relative to the turbulent momentum diffusivity.