A simplified approach to predict friedman curl effect in a solid rocket motor using ROBOOST simulation tool

In the design and development of solid propellant rocket motors (SRMs), the use of numerical tools able to simulate, predict and reconstruct the behavior of a given motor, in all its operative conditions is fundamental: more accurate performance predictions would reduce the need of expensive testing, thus lowering the cost of development for each SRM. This paper is intended to provide a simplified physical model to predict the pressure peak close to tail-off phase, namely Friedman Curl effect. This phenomenon depends on many factors, which are analyzed and discussed. The equations numerical treatment is explained in detail. Comparing between simulations and experimental results is carried out. Simulations are obtained with ROBOOST (Rocket BOOst Simulation Tool), a ballistic simulator developed at the Laboratory of Propulsion and Mechanics of the University of Bologna in collaboration with AVIO S.p.a.