ID 133

Size-Velocity pdfs for Drop Fragments Formed via Bag Breakup

 

Abstract:

Understanding secondary atomization of droplets directly relates to optimizing aircraft engine performance, pharmaceutical tablet coating efficiency, and agrochemical spray drift. Large droplets lead to lower fuel economy and higher pollutant emissions in aircraft engines. Optimizing pharmaceutical tablet coating drop size will improve drug uptake and patient comfort. Finally, agrochemical usage and spread can be better predicted and mapped to limit the spread into surrounding residential and environmental zones. Digital in-line holography (DIH) was used to capture high resolution, three-dimensional videos with high framing rates (20 kHz) using a 5 cm diameter laser beam and a high-speed camera (SA-Z). The apparatus followed that of Guildenbecher et al. (2016) and consisted of a CW laser, spatial filter, collimator, and included the air jet and drop generator described by (Guildenbecher and Sojka, 2011). The air jet had a nearly uniform velocity profile, while the drop generator was positioned to release 3 mm diameter drops above its centerline. The initial height of the drop was chosen such that the breakup processes were similar to those for a shock tube (Guildenbecher et al., 2009). Drop We was varied from 11 to 30 by changing the air jet velocity. The DIH holograms contained 3D fragment sizes and positions during breakup. Fragment velocity was determined from positions in adjacent image pairs for each reconstructed hologram using HoloSAND (Guildenbecher, 2015). The DIH data were used to create pdf(d,V). Results were plotted against drop We as they pertain to primary physical characteristics and trends that are discussed.