Wolfgang Black

Computational study of the shock driven instability of a multiphase particle-gas system

This paper considers the interaction of a shock wave with a multiphase particle-gas system which creates an instability similar in some ways to the Richtmyer-Meshkov instability but with a larger parameter space. As this parameter space is large, we only present an introductory survey of the effects of many of these parameters. We highlight the effects of particle-gas coupling, incident shock strength, particle size, effective system density differences, and multiple particle relaxation timeeffects. We focus on dilute flows with mass loading up to 40% and do not attempt to cover all parametric combinations. Instead, we vary one parameter at a time leaving additional parametric combinations for future work. The simulations are run with the Ares code, developed at Lawrence Livermore National Laboratory, which uses a multiphase particulate transport method to model two-way momentum and energy coupling. A brief validation of these models is presented and coupling effects are explored. It is shown that even for small particles, on the order of 1 μm, multi-phase coupling effects are important and diminish the circulation deposition on the interface by up to 25%. These coupling effects are shown to create large temperature deviations from the dusty gas approximation, up to 20% greater, especially at higher shock strengths. It is also found that for a multiphase instability, the vortex sheet deposited at the interface separates into two sheets. Depending on the particle and particle-gas Atwood numbers, the instability may be suppressed or enhanced by the interactions of these two vortex sheets.

Effect of Hydrophilic Nanostructured Cupric Oxide Surfaces on the Heat Transport Capability of a Flat-Plate Oscillating Heat Pipe

With a surface treatment of hydrophilic cupric oxide (CuO) nanostructures on the channels inside a flat-plate oscillating heat pipe (FP-OHP), the wetting effect on the thermal performance of an FP-OHP was experimentally investigated. Three FP-OHP configurations were tested: (1) evaporator treated, (2) condenser treated, and (3) untreated. Both evaporator- and condenser-treated FP-OHPs show significantly enhanced performance. The greatest improvement was seen in the condenser-treated FP-OHP, a 60% increase in thermal performance. Neutron imaging provided insight into the fluid dynamics inside the FP-OHPs. These findings show that hydrophilic nanostructures and their placement play a key role in an OHPs performance.