Comparison of Hull Hydrocode Computations of Shock Tube Blockage Effects on Target Loading for Step Shocks and Rapidly-Decaying Shocks

The HULL hydrocode was used to make two-dimensional calculations (for the three-dimensional axisymmetric problem) of a rapidly-decaying shock wave striking a finite right-circular cylinder whose axis was coincident with that of a cylindrical shock tube. Calculations were made for three peak shock over- pressures for 20 percent blockage and for a free-field encounter. These results were then compared with previously reported HULL computations for comparable overpressure step shocks for the same configuration. The net axial loading for these rapidly-decaying shocks behaved quite differently from that for the step shocks. It became negative early in the drag phase for the shock/target encounter in the free field, and oscillated about a net negative value in the drag phase. Net impulse showed a corresponding decrease (from a peak after the end of the diffraction phase) for the decaying shocks. Net impulse increased monotonically for the step shocks.