MEASUREMENTS OF AIR-BLAST PHENOMENA WITH SELF-RECORDING GAGES
The self-recording mechanical gages developed for recording overpressure and dynamic pressure as functions of time were installed on l2 shots. For several shots more than one blast line was instrumented. In addition to these blast lines, gage stations were prepared in locations to meet specific data reqwiirements, such as in the vicinity of structures, and in particular on a circle of gages at a radius of 2500 feet on Shots 12 and 14. Furthermore, a very- low-pressure gage was employed to record the wave shapes and magnitudes at large distances from the explosions. Particular application of this gage was made on Shot 10. The gages performed well, and the results were a wealth of data on a wide range of yields for a variety of surface conditions. Tabulations are presented of peak overpressure, positive-phase duration and arrival times at ground surface, and peak dynamic pressure, peak total - overpressure, and peak static overpressure at the 3-foot level. The curves for peak overpressure and peak dynamic pressure as functions of distance are shown plotted as observed and reduced to 1 KT at sea level in comparison with appropriate curves from TM 23-200 and ideal pressuredistance curves. Comparisons are shown between gage results under a smoke layer and on clear desert for Shot 5, between gage results on asphalt and desert surfaces of Shot 6, and between gage results on asphalt, desert, and water surfaces of Shot l2. Comparisons are also made of gage results of various shots with similar conditions. The data indicated that precursors formed on all shots instrumented except the first: gage failure to record pressuretime histories provided no data for determining precursor forrmation on this shoi. Precursor fornnation over asphalt was more pronounced than over the desert or water suriace. The rate of propagation and the positive phase duration were increased and overpressures decreased on the asphalt more than on the desert or the water surface. The good-surface-condition curve and the poor- surfacecondition curve of TM 23-200 bracketed the measured overpressure curves within the precursor zone. The more pronounced the precursor, the greater is the depression of the measured overpressure-distance curve. The smoke layer during Shot 5 reduced the thermal effects. The presence of a precursor affecting shock- wave parameters will depend hr:r suriace conditions and the height of burst and yield of the weapon or device. The enhancement of dynamic pressure will depend on surface conditions and is related to the depression of the overpressure- distance curve. An analytical method was used which describes the differences betwween tire measured dynamic pressure and ideal dyuamic pressures. This method can be used to predict fairly well the dynamic pressures over an asphalt surface but will underestimate the dynamic pressure over a desert surface. (auth)
- Research Organization:
- Ballistic Research Labs., Aberdeen Proving Ground, Md.
- NSA Number:
- NSA-16-003188
- OSTI ID:
- 4832023
- Report Number(s):
- WT-1155
- Country of Publication:
- United States
- Language:
- English
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