Aminian Manuchehr, Bernardi Francesca, Camassa Roberto, Harris Daniel M, McLaughlin Richard M
Department of Mathematics, University of North Carolina at Chapel Hill; Department of Mathematics, Colorado State University.
Department of Mathematics, University of North Carolina at Chapel Hill.
J Vis Exp. 2018 May 1(135):57205. doi: 10.3791/57205.
A simple method to experimentally observe and measure the dispersion of a passive tracer in a laminar fluid flow is described. The method consists of first injecting fluorescent dye directly into a pipe filled with distilled water and allowing it to diffuse across the cross-section of the pipe to obtain a uniformly distributed initial condition. Following this period, the laminar flow is activated with a programmable syringe pump to observe the competition of advection and diffusion of the tracer through the pipe. Asymmetries in the tracer distribution are studied and correlations between the pipe cross-section and the shape of the distribution is shown: thin channels (aspect ratio << 1) produce tracers arriving with sharp fronts and tapering tails (front-loaded distributions), while thick channels (aspect ratio ~1) present the opposite behavior (back-loaded distributions). The experimental procedure is applied to capillary tubes of various geometries and is particularly relevant to microfluidic applications by dynamical similarity.
描述了一种在层流中通过实验观察和测量被动示踪剂扩散的简单方法。该方法首先将荧光染料直接注入装满蒸馏水的管道中，使其在管道横截面上扩散以获得均匀分布的初始条件。在此之后，用可编程注射泵激活层流，以观察示踪剂在管道中的平流和扩散竞争。研究了示踪剂分布的不对称性，并展示了管道横截面与分布形状之间的相关性：细通道（纵横比<<1）会产生示踪剂以尖锐前沿和逐渐变细的尾部到达（前端加载分布），而粗通道（纵横比~1）则呈现相反的行为（后端加载分布）。该实验程序应用于各种几何形状的毛细管，并且通过动态相似性与微流体应用特别相关。
