Rarefaction Wave Eliminator Design Study
Final rept. 18 Sep 1987-15 Jul 1989
APPLIED RESEARCH ASSOCIATES INC LAKEWOOD CO
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Active and passive Rarefaction Wave Eliminators RWE were investigated for use on a small shock tube. An active RWE with rotation louvers for a modest size BRL shock tube was designed, with the open are versus time setting based on requirements from free-jet theory and the Random-Choice Method. This design yielded a device which met the operational requirements of completely closing within the 30 ms time duration of the positive phase of the simulated blast wave, and thereafter opened for the negative phase. The RWE was installed and tested at three blast wave overpressures. The results with the RWE are compared to those for both an open channel end and an extended channel on the shock tube, in order to evaluate the RWE performance. The experimental results showed that the preprogrammed theoretical area closing function was fairly accurate, especially at the lower overpressure levels. The predicted area setting is not accurate for the first few milliseconds after the shock arrives at the RWE, when the shock-induced outflow is inherently unsteady prior to the establishment of a semi quasi-steady jet outflow. Extrapolation of the small scale RWE design was made to the Large Blast and Thermal Simulator concept as well as the determination of preliminary costs.
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