Periodic boundary conditions in a 3D hydro code

We have modified a 3D hydrodynamics code so that it has the capability to impose periodic boundary conditions on the problem being considered. This capability allows it to treat only a basic symmetry unit of the problem when translational or rotational periodic symmetries are present. The code has been run successfully for two test problems involving rotational symmetries

Turbulent mix study of a double shell capsule

Double shell capsules present an alternative, non-cryogenic design for NIF ignition targets. Such capsules have received little interest because it was assumed that hydrodynamic instabilities would forestall ignition. The authors used a K-L turbulent mix model, integrated into a hydro code, to evaluate a series of double shell implosions. The double shell implosions were laser-driven experiments performed at the OMEGA laser. They briefly review the turbulent mix model. The model has adjustable parameters for the growth and dissipation terms. These are initially set by comparison to classical experiments. The model also requires an initial length scale and an initial wavelength scale. Next the authors briefly describe the experiment. The target assembly consists of an inner shell of glass and an outer shell of brominated plastic. They present the analysis of the hydrodynamic implosion, using the turbulent mix model. The agreement between experiment and calculation suggests that the model could be successfully applied to ignition targets

Modeling the interacting detonation fronts observed by low energy radiography

We have completed a series of experiments in which we made radiographs of interacting detonation fronts in a high explosive. Although the fronts and interactions were observed, the experimental data were insufficient to distinguish between two computer models which we employed to simulate the experiments

Electromagnetic velocity gauge: use of multiple gauges, time response, and flow perturbations

We have developed an in-situ electromagnetic velocity (EMV) gauge system for use in multiple-gauge studies of initiating and detonating explosives. We have also investigated the risetime of the gauge and the manner in which it perturbs a reactive flow. We report on the special precautions that are necessary in multiple gauge experiments to reduce lead spreading, simplify target fabrication problems and minimize cross talk through the conducting explosive. Agreement between measured stress records and calculations from multiple velocity gauge data give us confidence that our velocity gauges are recording properly. We have used laser velocity interferometry to measure the gauge risetime in polymethyl methacrylate (PMMA). To resolve the difference in the two methods, we have examined hydrodynamic and material rate effects. In addition, we considered the effects of shock tilt, electronic response and magntic diffusion on the gauge's response time

Hugoniots of aerogels involving carbon and resorcinol formaldehyde

Recently, a first-order phase transition is predicted in liquid carbon using atomistic simulation and Brenner's bond order potential. There are also experimental data suggesting a possibility for a first-order phase transition. In light of this, a thermochemical equilibrium code (CHEQ) is used to provide guidance to experiments to find a liquid-liquid phase change in carbon foam and carbon-rich aerogel, resorcinol formaldehyde. Isotherms and Hugoniots were computed based on the previous analysis by van Thiel and Ree. The present calculations predict the liquid-liquid-graphite triple point to be at 5000 K and 5.2 GPa and its critical point to be at 6000 K and 8.8 GPa. The present Hugoniot calculations suggest that the liquid-liquid phase transition may be detected by performing a shock experiment with initial density of approximately 0.15 gm/cm{sup 3}