Background-oriented schlieren measurements for gas-detonation-powered pressure relief systems in the free field

Abstract This paper presents the application of background-oriented schlieren (BOS) to obtain a quantitative characterization of shock waves from a free-field outdoor pressure relief system. A BOS setup was constructed, and an investigation was carried out to examine the influence of the background. Although critical locations in the natural background were identified, they could not be eliminated due to their large number, so an optimized random dot pattern was used instead. The evaluation method also took into account the intense radiation from the high-enthalpy gas flow. The aim was to visualize the shock wave front and reconstruct the shock wave front overpressure field. To this end, a linear calibration was performed between the optical results and those of the subsidiary pressure sensors. The estimated peak overpressures showed a good agreement with the measured values, with the BOS-based estimates slightly underpredicting the measurements. The maximum observed deviation was 8%. Therefore, this approach allows peak overpressure to be determined even at locations where no physical pressure sensors can be installed due to experimental restrictions, thereby extending the measurement capability of the experimental setup.