Flow turning in solid-propellant rocket combustion stability analyses

Culick developed the concept of a flow-turning effect from a comparison of the oneand threedimensional models of acoustic stability of combustion in a solid-propellant rocket motor. Several terms occur in the one-dimensional model which are absent from the three-dimensional model. Culick suggested adding these terms to the three-dimensional model in an ad hoc manner, arguing that they represent physical phenomena which are not accounted for in the analysis. A procedure is developed here to allow comparison of the oneand three-dimensional models by averaging over the cross section of the motor activity. This procedure results in the missing terms arising naturally as a result of the inclusion of the three-dimensional boundary conditions in the averaging process. This result raises serious questions concerning the ad hoc inclusion of terms into the threedimensional stability analysis without a clear physical basis.