Alan C. Calder

 

Astrophysical Thermonuclear Flashes

I am currently a research associate at the Center for Astrophysical Thermonuclear Flashes at the University of Chicago. The goal of the ASCI Flash center is to address astrophysical problems that involve thermonuclear flashes. Problems we are addressing include type I supernovae, novae, and x-ray bursts. There are many interesting projects in progress here, including research into flames, combustion and tubulence.

Part of our effort involves code validation tests. Click here to see a movie of a three dimensional simulation of a Rayleigh-Taylor instability. Click here to see a close-up movie of that simulation. Click here to see a movie of a slice plane of the simulation. These results come from the visualization magic of Dave Bock at NCSA. Details of his visualization of this simulation on its AMR mesh may be found here. Currently we are working on performing RT simulations from a particular set of initial condtions. The idea is to investigate alpha, the efficiency of potential energy release. There is a working page available. The image at the left is plot of density from a FLASH simulation of a Rayleigh-Taylor instability. A denser fluid (red) is initially at rest above a lighter fluid. The configuration is unstable, and in time fingers of the denser fluid penetrate the lighter fluid while bubbles of the lighter fluid rise into the denser fluid.

Recently I have been working on simulating laser driven shock experiments. The simulations we are working on currently have laser-driven shocks hitting multi-layer targets. The idea is to look for fluid instabilities that develop at the material interfaces as the shock passes through the materials. The image on the right is from a simulation of a laser pulse hitting a copper target that has an interface with CH2 plastic. The interface has a serveral-wavelength sinusoidal perturbation, and as shock passes through the interface, the instabilities are seen as plume of copper (reddish regions) and bubbles of plastic (green/yellowish regions). The purple region to the left is low density material ablating to the left. Click here to see a movie. The simulation treats the copper and CH2 as ideal gasses, each with a fixed gamma.

The image below is from a 3-layer target simulation. The laser beams were incident on the left, and drive a shock through a region of copper that borders a region of plastic. The plastic borders a region of foam on the side opposite that of the copper.

The copper/plastic interface initially has a sinusoidal perturbation. In this simulation the perturbation corresponded to one wavelength, so that after 65 ns we see one spike of copper protruding into the plastic. The interace between the plastic and foam is initially smooth. As can be seen in the image, a bubble of foam rises into the plastic as the shock passes through. Future simulations will include a more realistic equation of state. As with the RT work, there is a working page available.

 

Astrophysical Thermonuclear Flashes
Neutron Star Mergers
Core Collapse Supernovae

 

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Last modified: December 12, 2006