基于micro-PIV的微通道内流体绕流单微圆柱和并联双微圆柱流场特性

Analysis of fluid across a single cylinder and two parallel cylinders in a micro flow channel by micro-PIV

采用微观粒子图像测速(micro-PIV)技术对微通道内单微圆柱和并联双微圆柱绕流流场特性进行研究,通过对不同雷诺数(Re)下单微圆柱和并联双微圆柱绕流流场的观测,分析Re对速度场、涡量强度、相位角和涡的量纲为1长度的影响规律。通过实验研究发现:微纳尺度下圆柱绕流的漩涡形成和脱落相比于宏观尺度下圆柱绕流具有一定的迟滞性。并联双微圆柱的迟滞性大于单个微圆柱。随着Re的增加,漩涡的长度和宽度随着增加,涡量带向微圆柱下游方向延伸得更远。相位角和漩涡的量纲为1长度随之增加。并联双微圆柱漩涡结构发生变形,呈现鼓状。受到主流区的影响,漩涡的结构受到挤压,呈带状漩涡,同时,焦点的位置向两圆柱中心水平线的方向偏移。随着Re的不断变大,量纲为1涡长和相位角整体呈上升趋势,并联双微圆柱中,受到两微圆柱之间主流区的影响,上微圆柱的相位角整体大于下微圆柱。

The micro particle image velocimetry(micro-PIV)technique was used to study the flow field characteristics of single and parallel double micro-cylindrical bypass flow in microchannels.The effect of Re on the velocity field,vortex intensity,vortex angle and vortex dimensionless length was analyzed by observing the single and parallel double micro-cylindrical bypass flow fields at different Reynolds numbers(Re).The experimental study revealed that the vortex formation and shedding of cylindrical winding flow at the micro-nano scale had a certain hysteresis compared with that of cylindrical winding flow at the macroscopic scale.The hysteresis of parallel double micro-cylinders was larger than that of single micro-cylinders.The length and width of the vortex increase with increasing Re,and the vortex volume band extended further downstream of the microcylinder.The vortex angle and the dimensionless length of the vortex also increased with Re.The parallel double microcylinder I vortex structure was deformed and showed a drum shape.Affected by the mainstream region,the vortex structure was squeezed and showed a band vortex,while the position of the focal point was shifted toward the direction of the horizontal line of the center of the two cylinders.With the increasing of Re,the dimensionless vortex length and vortex angle showed an overall increasing trend.