Image-Based Analysis of Interactions Between a Steady Jet and an Impulsively Started Jet

Ignition overpressure (IOP) is a principal dynamic load experienced by a launch vehicle during liftoff. The IOP arises due to the sudden ignition of the solid rocket boosters (SRBs) of a launch vehicle. The present work attempts to simulate the ignition of an SRB with an impulsively started supersonic M d = 2.0 jet generated using a quick-open valve. High-speed schlieren flow visualization is used to document the evolution of an impulsively started jet flowfield that included the characteristic precursor shock wave (that simulates the blast wave causing the IOP) and the following vortex ring. The dynamic interactions between the impulsively started supersonic jet and an established steady supersonic jet from another nozzle ( M d = 2.0 ) in close proximity are also investigated. Both the precursor shock wave and the vortex ring interact strongly with the established steady-jet column as they proceed downstream from the nozzle exit, thereby introducing new sources of acoustic waves. When a generic jet blast deflector is introduced downstream of the nozzles, the precursor shock wave reflected from it, propagating upstream toward the nozzle exit. The reflected shock wave is recognized as the source of IOP experienced by the launch vehicle. The results show that the quick-open valve presents a unique way to generate impulsively started jets for understanding transients associated with the ignition of the SRB leading to the IOP, without the complexity associated with the use of open-ended shock tubes for carrying out such simulations.