Secondary Waves from Nozzle Blast
Final technical rept.
ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE CALIBER WEAPON SYSTEMS LAB
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Blast signatures at the gunners position produced by recoilless rifles and rocket launchers often exhibit a strong secondary wave following chamber blowdown. To identify its source a series of experiments was performed using a helium-driven blast simulator. The resulting pressure traces and shadowgraphs show the wave emerging from the portion of the plume just aft of the nozzle, but leave unexplained its relationship to the plume flow field structure. This information was obtained from a numerical solution of the Euler equations using Hartens Total Variation Diminishing TVD scheme. Based on this data, contour and surface plots of pressure were constructed which reveal quite clearly the plume wave structure and its response to the falling chamber pressure. A secondary wave emerges from the same region of the plume as it did in the experiment.