Advances in Engineering Advances in Engineering features breaking research judged by Advances in Engineering advisory team to be of key importance in the Engineering field. Papers are selected from over 10,000 published each week from most peer reviewed journals.
Carroll, Brian; Hidrovo, Carlos
Experiments in Fluids, Volume 53, Issue 5, pp.1301-1316
Multiscale Thermal Fluids Laboratory, University of Texas at Austin, Austin, TX, USA
Abstract
A novel droplet mixing measurement technique is presented that employssingle fluorophore laser-induced fluorescence, custom image processing, and statistical analysis for monitoring and quantifying mixing in confined, high-speed droplet collisions. The diagnostic procedure captures time-varying fluorescent signals following binary dropletcollisions and reconstructs the spatial concentration field by relatingfluorophore intensity to relative concentration. Mixing information is revealed through two governing statistics that separate the roles of convective rearrangement and molecular diffusion during the mixingprocess. The end result is a viewing window into the rich dynamics ofdroplet collisions and a diagnostic tool that differentiates between poor and effective mixing. The technique has proved invaluable in the laboratory by allowing direct comparison of different hydrodynamic conditions, such as collision Reynolds and Peclet number, and collisiongeometries, such as T and Y-junctions. Experiments indicate improvedmixing rates and degree of homogenization as the convective timescale for the collision is decreased. Visualization of mixing residuals using pseudo color mapping also identifies areas that are largely segregated from the mixing process, resulting in islands where mixing is poor and stirring has proved ineffective. As the collision velocity is increased, vortical flow fields become apparent and mixing is greatly improved.
