Background Oriented Schlieren for Mixture ANalysis In Aerosols – BOS-MANIA

Many essential engineering applications that societies rely on daily are grounded in a precise understanding of spray dynamics. Improving the experimental analysis of spray liquid distribution and vaporization can yield substantial benefits across various fields, including agriculture, meteorology, medicine, and energy.
Two key parameters define the macroscopic mixing behavior of a dispersed-phase flow within a carrier fluid: the volume fraction of the injected liquid and the mass fraction of its vapor phase. Laser Induced Fluorescence (LIF) is currently the only technique capable of simultaneously measuring the spatial distribution of these two quantities in a two-phase flow. Although LIF is a powerful tool for providing instantaneous fields of mixture characteristics, its practical implementation is complex and costly, presenting several technical challenges.

This project aims to develop an alternative optical diagnostic technique to LIF for measuring macroscopic mixing in dilute flows. The objective is to create a method that is both cost-effective and easily adaptable to various experimental setups. To achieve this, the project proposes utilizing Background Oriented Schlieren (BOS), an affordable and optical diagnostic method that measures the deflection of light rays passing through a flow by detecting the apparent displacement of an illuminated background pattern.
Our proposal seeks to upgrade the existing optical setup and the post-processing chain of the BOS system to exploit both light deflection and extinction, enabling respectively he simultaneous quantification of the 3D distribution of the vapor phase mass fraction and liquid volume fraction in evaporative dilute flows. The technique will be validated through a joint experimental-numerical investigation of a fully characterized spray injected by a simplex atomizer, and will subsequently be applied to study the formation and propagation of helical mixture waves in a swirl-stabilized spray.