Linear analysis of forced longitudinal waves in rocket motor chambers

A methodology centered around the forced longitudinal wave (FLW) motor is being developed to investigate dynamic responses of rocket motors. The FLW motor establishes periodic longitudinal pressure and velocity oscillations in solid propellant rocket chambers. A linear analysis was developed to study propellant pressureand velocity-coupled responses using dynamic pressure measurements at several locations in a motor. The analysis uses pressure amplitude and phase measurements. Variations in the propellant reponses are shown to produce measurable changes in the calculated oscillating pressures with velocity-coupled responses showing the greatest promise for determination from experimental data. Experimentally deduced velocity-coupled response functions are examined over a frequency range centered around the chamber fundamental mode for a range of interior flowfields and chamber pressures for 86%AP-14%HTPB propellants.