Numerical Analysis of Ignition Overpressure Effect on H-IIB Launch Vehicle

A numerical simulation was conducted to investigate the ignition overpressure mechanism generated by the Japanese H-IIB launch vehicle. A simplified benchmark problem and analysis of a free jet exhausted from a single solid booster were used to verify the present numerical method; the unsteady Reynolds-averaged Navier-Stokes simulation was found to be essential for determining the typical features of ignition overpressure, such as the shock wave generated in front of the plume and following starting vortex. Comparing with the measured pressure history at the launch complex, the numerical result agreed reasonably. The correlation between the wave pattern measured at the launch complex and the ignition overpressure mechanism was clarified. The effect of ignition overpressure on the launch vehicle can be reduced by shielding the inlet of the flame duct with a mobile launcher; however, severe impact on the launch complex is unavoidable. The numerical technique and knowledge obtained in this study are applicable in the preliminary design of a launch pad to mitigate the impact of ignition overpressure.