Alston S. Householder Fellow explores explosive issues
Posted February 4, 2008
Even if Ralf Deiterding had gazed into a crystal ball when deciding what
to study in his native Germany, he couldn’t have made a better choice
for the work he does today.
“My diploma is in applied and technical mathematics,” says Deiterding. “It’s 60% math, 20% computer science and 20% mechanical engineering. I focused on solid mechanics and fluid dynamics.”
It’s ideal for his current job: simulating detonation and shock waves in various scenarios at Oak Ridge National Laboratory (ORNL). Deiterding holds the Alston S. Householder Postdoctoral Fellowship in Scientific Computing, which is supported by DOE’s Office of Advanced Scientific Computing Research.
Deiterding’s work combines a number of disciplines: developing and applying innovative numerical methods, scientific computing on high-performance DOE supercomputers, visualizing results, and interpreting physical phenomena.
In one ASCR-supported project, Dieterding and his fellow researchers are creating a high-resolution simulation of a detonation wave in a hydrogen-oxygen gas mixture to better understand the underlying mechanisms of possible explosions in refinery pipelines.
Studying Shock
A detonation is a combustion wave caused by a shock. Compression from the shock raises the temperature above the ignition point for the chemical reaction that drives combustion – it is that reaction that drives the shock itself forward. The energy balance between the shock and the chemical reaction is unstable, so detonation waves don’t remain in a single plane.
“Unstable shock waves spread perpendicular to the detonation front,” Deiterding explains. “You get triple points – places where the detonation front and transverse shocks intersect. At these points, pressure can increase by a factor of five and temperature rises as well.”
Experimental work shows that the triple points often move in “fish-scale” patterns. The rotational flow of the fluid increases locally, which researchers can use to track the triple points. The key to accurately simulating detonations – and, in the end, to making pipe installations safer – is correctly tracing the evolution of these areas. In fact, one reason Deiterding is confident in his simulation results is that the same number of triple points reappear after the bend.
