1». SUPPLEMENTARY NOTES 19. KEY WOROS (Continue on WWW aide It neceemmry end Identity by block number) shock tube blockage shock tube HULL hydrocode blast simulator step shocks blast loading decaying shocks 20. ABSTRACT (Corrttoue en revere* etam ft IMCMMTT f Identity by block number) 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

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... with that of a cylindrical shock tube. Calculations were made for three peak shock overpressures for 20 percent blockage and for a free-field encounter. These result^ were then compared with previously reported HULL computations for comparable DD/^1473 EDITION OF » MOV 65 IS OBSOLETE UNCLASSIFIED SECURITY CLASSIFICATION OF TNIS PAGE (When Date Enteret!) UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGEfWhan Dmtm Bntrntrnd) 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. Flow conditions in the constricted region were enhanced for the decaying shocks. Although the relative enhancement at late time was large compared with values for the same decaying-shock/target interaction in the free field, it was an enhancement of relatively small values of velocity and dynamic pressure in an absolute sense. Hence, the effect of the 20 percent blockage on target loading from the rapidly-decaying shocks studied here was unimportant, except for shock reflections from the shock tube wall early in the drag phase. ^r.^.=--~*tcp-UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGEr»W«en Dmtm Entmrmd)