Detonation waves are complicated by the presence of liquid or solid fuel particles. Under detonation conditions liquid fuel droplets must breakup, vaporize, and react rapidly.
Research
Shock-Driven Multiphase Instability
The Shock-Driven Multiphase Instability (SDMI) occurs when a multiphase flow field with strong gradients in particle parameters (e.g. number density or diameter) is accelerated by a shock wave. This acceleration deposits vorticity at the interface which causes the multiphase flow field to mix.
Astrophysical Hydrodynamics and Instabilities
Dust being ejected by stars leads to an interesting multi-physics problem. We simulate the transport of this dust and track the hydrodynamic development of the gas and dust over large domains and time periods.
Details
Stellar luminosity variations and dust hydrodynamics in Asymptotic Giant Branch (AGB) stars, and the consequences for dust survival and mass-loss, remain elusive. We broadly investigate the role of dust and radiation hydrodynamics in the formation of dust and gas structures, heterogeneous clumps, observable in AGB remnants, and planetary nebulae (PNe). Spatial perturbations arise due to luminosity variations from turbulent thermal convection within the star and stellar atmosphere. These variations in the radiation field drive spatial perturbations of the dust and gas field and may be responsible for the formation of larger clumps, such as cometary knots, seen in the PNe phase. We use FLASH for studying this problem at large length and time scales. Simulations are performed in 2D solving the Euler equations with source terms resulting from the particle phase, represented by free Lagrangian points. We implement radiation coupling for the particle phase, modeling radiation heating and acceleration of the particles, and subsequent coupling to the gas phase through non-continuum heat and momentum transfer models.
Research is done in conjunction with Dr. Angela Speck at the University of Texas, San Antonio.
Ejecta Transport and Breakup
Ejecta are small particles released from an intensely shocked material’s surface defects. The subsequent transportation and breakup, especially during the secondary breakup process, creates an interesting multiphysics problem which involves hydrodynamics, chemical reactions, and multiphase materials.
Description
Ejecta are small particles within an impulsively driven flow. Of importance to the research at FMECL is the study of ejecta that propagate from a material when the surface is rapidly accelerated, such as during an intense shock. In this case, a shock driven Richtmyer-Meshkov instability causes the initial ejecta release from the material, in which the shock wave interacts with the small imperfections on the surface of the material. Such shocks are often intense enough to cause some sort of melting of the material, creating a difficult multiphysics problem that involves the considerations of multiphase materials, hydrodynamics, heat and mass transfer, and chemical reactions.
Studies on ejecta are also found in volcanic explosions, astrophysics, respiratory events, and other high-energy applications.
Images
Velocity and temperature fields for a resolved simulation of solid particle shock acceleration. [1]
Further Reading
- Maxon, W. C., Nielsen, T., Denissen, N., Regele, J. D., and McFarland, J. (April 9, 2021). “A High Resolution Simulation of a Single Shock-Accelerated Particle.” ASME. J. Fluids Eng. July 2021; 143(7): 071403. https://doi.org/10.1115/1.4050007
Past Research Projects and Topics
Magnetohydrodynamic Richtmyer-Meshkov Instability
The Richtmyer-Meshkov Instability occurs when an interface between fluid of different densities is accelerated by a shock wave. When one or both of these fluids is conducting, it can react to the presence of a magnetic field. The resulting magnetohydrodynamic effects can suppress the mixing normally observed in the Richtmyer-Meshkov Instability.