Numerical Simulation of Laser-Induced Drop Evaporation
Abstract
Despite the rapid development of naval laser weapon systems, applications used to model High-Energy Lasers (HEL) in maritime environments are still incomplete. When a high-energy laser interacts with raindrops, fog, or other aqueous aerosols, the laser propagation and drop thermodynamics are coupled through the absorption-dependent vaporization process. Experiments with small droplets have shown that laser-droplet interactions may fall in two regimes a slow heating regime where the drop rapidly evaporates due to elevated surface temperature, and a fast heating regime where the drop explosively breaks apart due to the pressure wave from spontaneous vaporization. Related numerical studies have ignored internal drop dynamics, assuming either spatially isothermal drops or assuming that heat transfer is by diffusion only. Recent experiments with larger laser-irradiated drops have shown that temperature fluctuations and internal drop dynamics are not negligible when drop diameter is on the order of 1 mm, e.g. in rain or sea spray. These Experiments measured drop surface temperatures during a slow heating regime, but were unable to measure temperatures on the interior of the drop, where spontaneous vaporization is most likely to occur. This research uses computer simulations to explore the laser heating, fluid dynamics, and evaporation of large water drops in order to determine internal drop temperatures and predict the onset of a fast heating regime. Simulations are run using COMSOL Multiphysics, a commercial solver based on the Finite Element Method. A geometric (ray) optics approach is used to generate internal volumetric heating distributions within a drop. This heating distribution is then applied to drops with different shapes and sizes, with increasing physical complexity to evaluate the effects each physical assumption has on the drop dynamics.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 20, 2019
- Accession Number
- AD1073959
Entities
People
- Stefano Pineda
Organizations
- United States Naval Academy