Velocity measurements in single and parallel channels using concentration changes in aqueous methylene blue solution

Fluid flow along a path confined by a solid wall is observed in various industries, ranging from microfluidic channels to industrial piping systems. A straightforward technique is needed to measure the velocity in a branched channel system. This study proposes a non-invasive method for measuring the velocity in opaque parallel channel flows under laminar flow conditions. An aqueous methylene blue solution was infused into a channel with a square cross-section prefilled with deionized water, allowing for measuring the velocity field based on variations in liquid concentration. The proposed technique was tested in several configurations: a straight single channel, parallel channels with varying numbers of flow paths and inlet distribution lengths. As the number of flow paths for the parallel channel increased and the inlet distribution length decreased, a non-uniform flow distribution was observed. In all cases, the experimental results were in good agreement with the simulation results.