Flow dynamics at the minimum starting condition of a supersonic diffuser to simulate a rocket’s high altitude performance on the ground

A numerical analysis was conducted to investigate and characterize the unsteadiness of the flow structure and oscillatory vacuum pressure inside of a supersonic diffuser equipped to simulate high-altitude rocket performance on the ground. A physical model including a rocket motor, vacuum chamber, and diffuser, which have axisymmetric configurations was employed. Emphasis was placed on investigating the physical phenomena of very complex and oscillatory flow evolutions in the diffuser operating very close to the starting condition, i.e. at a minimum starting condition, which is one of the major important parameters from a diffuser design point of view.