双重裂隙介质内微观粒子测速研究

Micro particle velocity measurement in dual-scale fracture network microfluidics

微流控实验结合微观粒子图像测速技术(μPIV)是解析孔隙尺度复杂流体流动过程的重要手段。裂隙介质中存在不同大小的裂隙结构,影响溶质运移等行为。为探究复杂裂隙结构对μPIV测速结果的影响,该文设计了双重裂隙网络结构,以此对比μPIV粒子测速结果和孔隙尺度模型模拟结果。结果显示:主裂隙中μPIV测速结果与孔隙尺度模型模拟结果基本一致;微裂隙中粒子运动受边界影响较大,且优势通道的存在使进入微裂隙内的粒子数较少,导致部分区域测速结果与模拟结果存在较大偏差。该文总结了复杂介质结构中使用μPIV进行粒子测速可能导致偏差较大的区域并分析其成因,为提高μPIV粒子测速的准确性提供了新的认识。

Micro-particle image velocimetry(μPIV) used in microfluidics experiments is an emerging technique to capture pore-scale flow dynamics in porous/fracture media.Fractures with different sizes influence solution transport.In order to explore the influence of particle transport on the accuracy of the μPIV in complex fracture structures,a dual-scale fracture network microfluidics model is designed.Pore-scale flow fields are measured by μPIV and compared with those simulated by pore-scale models.The results show that,in general,the flow fields in the macro fractures measured by μPIV are consistent with pore-scale simulations.However,large deviations are observed for flow field in micro fractures because the number of particles entered into the micro fractures are less than expected,and their transport in micro fractures is greatly affected by the boundary conditions.This study provides technical references for μPIV measurements and the associated applications in complex fracture media.