Characterization of Aerodynamic Fragmentation of a Drop by Cross-beam Two-view Digital In-line Holography

Aerodynamic breakup of drops as a form of secondary atomization has wide scientific and engineering applications. Previous experimental studies using point-wise and two-dimensional (2D) measurement techniques are unable to provide three-dimensional (3D) spatially-resolved information about the breakup without significant experimental repetition. Digital in-line holography (DIH) has unique access to 3D information and has been demonstrated as a powerful tool for quantitatively characterizing aerodynamic fragmentation of a drop in the bag breakup regime. Using the technique, the size distribution, spatial distribution, 3D threecomponent velocities of drops and the morphology of the rim can be measured. However, in general the uncertainty of position measurement along the optical axis (depth) direction is difficult to analyze and tends to be considerably larger than the uncertainties in the in-plane directions. Here, a cross-beam two-view configuration is utilized to characterize the out-of-plane uncertainty of the single-view configuration and to improve the velocity measurement accuracy via matching the particles viewed from the two perspectives. Sequential holograms of the bag breakup process are recorded by cameras working in the double-exposure mode synchronized with double laser pulses. The droplets in sequential holograms are paired to calculate the 3D, three-component velocities. High-fidelity data of drop velocities are obtained using the stereo two-view method. The sizes of the drops due to the bag breakup and the rim breakup are also resolved. ∗Corresponding Author: [email protected]