Characteristics of Base Drag and Flow with Nozzle Flow Conditions in Supersonic Flow

The characteristics of base drag and base flow were analyzed with the free-stream Mach number, chamber pressure, and nozzle divergence angle, through computational simulations. The numerical technique was validated through a comparison with a wind tunnel test. The results showed that base drag was affected by the nozzle divergence angle, free-stream flow, chamber pressure, and base flow was affected by the interaction of free-stream flow and the recirculation region generated at the base. In the over-expanded and relatively low under-expanded conditions, the expansion fan affects base drag, and base drag tends to be higher as the nozzle divergence angle is smaller. However, the opposite occurs when the Mach number is sufficiently low. In the highly under-expanded condition, the shock wave affects base drag, and base drag tends to be higher as the nozzle divergence angle is smaller. However, the main factors that affect base pressure can be varied in the high Mach number.