Simulations of piston driven compaction waves in a granular bed of coarse grain HMX have been performed. Averaging the flow transverse to the propagation direction results in a smooth quasi-static wave profile. Weak partly compacted waves are fully dispersed while strong fully compacted waves have a wave width of 1 to 2 grain diameters. As expected the end states across a compaction wave obey the Hugoniot jump conditions. The temperature fluctuations behind the wave front are in the range that would affect ignition.
Hot spots can be much smaller than a grain diameter.
They are affected by dissipative mechanisms. The simulations include plastic work, frictional heating modeled as shear viscosity and bulk viscosity. The hot-spot distribution behind the compaction wave is discussed. For weak initiation, material strength hence plastic work and shear heating are important for generating hot spots. In the regime of prompt shock initiation, void collapse is the dominate mechanism for generating hot-spots.