Below are items from the 46th DCASS, held 2 March 2021. Note, this was held as a virtual event due to the global pandemic.
Riding the Silica Wave
Michael Wilkinson and Marina B. Ruggles-Wrenn
Air Force Institute of Technology
Borosilicate glassy layer on top of hafnium oxide scale, both of which are produced on the surface of hafnium diboride with 20 percent silicon carbide by volume after heated to 1600 degrees Celsius in air.
Interface Shape Between Liquid Drop and Layer
Murat Dinc
Miami University
It is very significant to differentiate liquid drop and liquid layer in single drop and spray cooling research areas to better understand the effects of liquid drop and layer on the results. One of the best way to do is using computer simulations to analyze liquid drop and liquid layer separately by assigning separate phases and colors for each. This image obtained from a 2D axisymmetric multiphase simulation of a single liquid drop impacting on a liquid layer. In this simulation, blue color represents liquid drop, green represents liquid layer, and red represents air phases. The shape of liquid drop at the simulation time shown in top image resembles moon jellyfish (blue liquid drop) whereas the shape of interface between the liquid drop and layer changes with simulation time and eventually liquid drop resembles octopus like shape with liquid crown sheet and waves that looks like octopus legs (bottom image).
Ceramics at the Center of the Sun
David Swanson and Marina B. Ruggles-Wrenn
Air Force Institute of Technology
A close-up view of a small oxide ceramic specimen as it undergoes a scorching heat treatment at 1500 degrees Celsius in a ceramic tube furnace.
Detonation Chamber Rapid Unplanned Disassembly
Daniel Cuppoletti
University of Cincinnati
An optically accessible detonation chamber undergoes rapid unplanned disassembly while investigating the physical mechanisms responsible for detonation amplification. A decelerating detonation wave travels from left to right and as it reflects from a wall it reinitializes the detonation which propagates back from the right in an amplified state, as indicated by the strong emission. The unsteady reinitialization of the detonation wave generates 2-3 times the pressure and temperature of a steady detonation, resulting in 1,500-2,000 psi for a few microseconds. This initiates a crack in the polycarbonate windows that propagates back across the test section and the window separates approximately 1 inch and comes back together, avoiding complete destruction from the bolts in the upper window hitting the rods holding the test section together and imprinting the thread pattern into the structure. Fortunately, we had more windows and now we have some fun desk hardware. Schlieren video captured at 175,000 fps, playback at 20 fps, over a 12 ms time period, false color applied.
Motion of Debris Following a Catastrophic Spacecraft
Mishap During an Earth-Moon Transfer
Nathan Boone and Robert Bettinger
Air Force Institute of Technology
This animation shows the motion of debris following a catastrophic spacecraft mishap during an Earth-Moon transfer much like the transfer used by the Apollo 13 mission. In this video, the green circle represents the Earth, the black circle represents the Moon, the red crosses represent the Earth-Moon Lagrange points, and the yellow line extends toward the Sun. The black dots represent debris particles generated in the spacecraft explosion. Debris enters an orbit with a perigee within the geostationary belt and an apogee well beyond the Moon, possibly suggesting threats to operational spacecraft near Earth if a debris-generating spacecraft mishap similar to the Apollo 13 event occurred today. Also interesting in this animation is the cardioid-like shape that forms at the apogee of the debris cloud, possibly reflecting the gravitational influence of the Moon.