Construction and Testing of the ARL 1.68-m Diameter Shock Tube Exit Jet Spreader for Non-Ideal Blast Simulation.

The U.S. Army Research Laboratory ARL has demonstrated the feasibility of fusing the modified exit jet of a simple shock tube to simulate high dynamic pressure air blast flows such as those that occur in non-ideal nuclear blast events. These flows can be used to generate simulated non-ideal blast loads on Army equipment with the intent of evaluating and improving its survivability. This work has included the use of small, intermediate, and large scale shock tubes to which exit jet spreader devices were incorporated. These spreaders were mounted at the ends of the shock tubes but were not directly connected to them. Their purpose was to spread the exit jets and their associated dynamic pressure impulses more uniformly over a greater area, thus providing a more accurate simulation capability for testing larger targets. This report documents some of the latest efforts by ARL in evaluating the use of modified shock tube exit jets for simulating non-ideal blast flow. Previous studies at ARL included the mapping of unspread exit jets at three different shock tube scaled sizes and the evaluation of exit jet spreaders at the two smaller shock tube sizes to evaluate the effectiveness of the various spreaders and determine the degree of uniformity of the spreading. In the latest effort, a full scale exit jet spreader has been constructed for use with the ARL 1.68-m diameter shock tube, the largest of the three shock tubes. Displacement experiments with World War 2 Army jeeps have been conducted to compare vehicle response to the dynamic pressure impulse loading generated by the spread jet of the shock tube with that from past actual and simulated nuclear tests in which jeep displacement data were obtained.