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Theoretical, Numerical and Experimental Investigation of Vortex Shedding in a Novel Sub-Scaled Motor
Author(s): Roohollah Taherinezhad, Gholamreza Zarepour
Keywords: pressure oscillation, vortex shedding, strouhal number, solid rocket motor
Pressure oscillations are one of the important challenges in segmented solid rocket motors with high slenderness ratio. Reason of these oscillations can be searched in vortex shedding due to grain burning areas, holes and slots. In this paper, the pattern of four segments grain of space shuttle boosters and structure of Ariane5 sub scaled motors has been used for evaluation of aero acoustic pressure oscillations. First, the related parameters to scale down using Buckingham’s Pi theorem were determined and then a sub scaled 1:31 motor was designed and manufactured. Going on, Strouhal number in various grain forms and vortex shedding prediction criteria was discussed. Next, for relative understanding of motor internal flow and vortex shedding formation, steady state computational fluid dynamic was done for seven regression steps and finally, for validation of analysis and simulation, two static tests performed. Results show that various definitions for Strouhal number is useful only for primarily glance on vortex shedding and pressure oscillations and so CFD solution and test program is inevitable for correct understanding of ballistic operational condition of motor. Also, despite of aggress of pressure test data curves and grain burning regression of sub scaled motor to full scale motor, internal flow phenomenon may be different due to small scale time and dimension with full scale motor.