Large Eddy Simulation Of Vortex Shedding For Solid Rocket Motor

Usually the large solid rocket motor is charged with segmented propellant grain and withsubmerged nozzle. The cavity of the submerged nozzle and the obstacle, such as the annularinhibitors which segment the propellant grain will cause the phenomenon of vortex shedding.Further the vortex shedding will result in the problems of pressure oscillation，combustioninstabilities，etc.In this thesis, numerical simulation method is adopted to investigate the phenomenon ofvortex shedding initiated by configuration of the obstacle and submerged nozzle in solidrocket motor.The k εequations of turbulent model ignores the existence of microvortexbecause of the viscous dissipation, so the turbulence model：large-eddy simulation based onsoftware FLUENT is used. The parametric studies with different cavity volumes, obstacleposition, obstacles size and velocity of far field have been conducted assuming the flow to beaxi-symmetric. Meanwhile, in order to reduce the calculation under the premise of ensuringthe calculation accuracy, models with different grid numbers are chosen and the calculatedresults of each model are compared. The calculated results in the thesis are consistent in thedata of literature and experiment, meaning that the methond took by the thesis is reasonable.The comparison of calculated results shows that in the premise of small y+, the gridnumber have little influence to the simulation result. The airflow will causes vortex on bothsides of the obstacle when it flows through the obstacle, and the phenomen of vortex sheddingwill happens at the top of the obstacle. In fact, in the cases of unchanged chamber size, thefrequency of vortex shedding will becomes larger with the increasing of the velocity of farfield and the radial characteristic scale of obstacle, it also becomes larger when the distancebetween the obstacle and the nozzle head and the volume of cavity decreases. At the sametime, it has approximate linear relationship with velocity of far field.