A computational study of the wave phenomenon and probable cavitation that occurs when a droplet interacts with a shock is presented. A volume-of-fluid method with and without a cavitation model activated is employed. The model with no cavitation is used to clarify the droplet's internal wave field. The model is benchmarked using experimental data of a 22 mm water column impacted by a shock wave at Mach 2.4. Good agreement between the computational results for a two-dimensional (2D) circular droplet and the experimental results is demonstrated. A simplified 2D, square droplet is also considered in order to highlight the effects of interface curvature on the internal waves. Comparison of the results for the square and circular drops shows that the circular geometry diffuses the initial pressure wave while focusing the reflected wave. The three-dimensional (3D) spherical droplet was then analyzed. The internal wave behavior is similar to the 2D circular drop with enhanced diffusion and focusing. Two cavitation models were then used to explore the probability that cavitation occurs for a nominal sized raindrop interacting with shock waves, Mach 1.5–5. Two cavitation models, full Rayleigh–Plesset (FRP) and Schnerr-Sauer both predicted vapor formation at the same location with the FRP always predicting slightly higher amounts of vapor. The current setting for number of nuclei ensures that the simulation is not swamped by vapor formation but is unrealistically small. Therefore, while the work demonstrates that cavitation will occur, the full nature of the cavitation along with the impulsive pressure waves it should create is not currently captured.
This paper presents a comprehensive study of viscoelastic, droplet-breakup physics using multiphase computational fluids dynamics (CFD) based on the volume of fluid (VOF) method. The specific challenge and novelty are the overall outcome and methods used to explore viscoelastic breakup physics. In the context of VOF, the method approximates both viscous and elastic characteristics of the saliva with a function based on the Carreau-Yasuda (CY) model. The CY model is traditionally used for modeling blood flow and here is extended to approximate saliva. The foundation of the model couples the shear rate to drive both a variable viscosity and relaxation time. The results indicate a strong stabilizing effect of viscoelastic fluids that indicates that conventional breakup models provide a conservative estimate of droplet size as is relevant to the transmission pathogens.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.