XHVRB reactive flow modeling of the PBX 9501 gap-stick experiment

The extended history variable reactive burn (xHVRB) model was recently calibrated using published data for PBX 9051, as reported elsewhere. Here, we have tested the model’s performance in the “Los Alamos Gapstick” configuration which consists of a cylindrical stack of explosive pellets separated by inert gaps of increasing thickness. The gapstick experiment probes the shock-to-detonation transition (SDT) behavior of the explosive, ranging from prompt detonation to detonation failure. While the xHVRB reactive flow model is calibrated using 1-D planar SDT data, the gapstick configuration tests the model behavior under conditions of highly curved and divergent two-dimensional shock waves. Our results show that the xHVRB model, as implemented in Sandia’s shock physics hydrocode, CTH, agrees with the published gapstick data for PBX 9501. We will also compare the xHVRB model results with the predecessor model, HVRB, and other reactive flow models such as ignition and growth (IGRB). Finally, we discuss the implications of the gapstick experiment and its potential applicability as a calibration experiment for explosive materials whose SDT behavior has not otherwise been characterized. [Acknowledgement: SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.]