Effects of geometric parameters on flow characteristics of multi-stream serpentine nozzle

The geometric design parameters exert a significant influence on the flow characteristics of multi-stream serpentine nozzles， including multi-stream mixing performance. To investigate the variation patterns of nozzle flow characteristics with geometric parameters， numerical simulations were conducted for multi-stream serpentine nozzles with different throat aspect ratios and offset ratios. The results demonstrate that the throat aspect ratio governs the pressure differential variation in the mixing section to regulate flow mixing effectiveness. Higher throat aspect ratios reduce the pressure difference between the lower wall surface and main flow in the mixing section， leading to decreased flow deflection angles. This enhances mixing completeness in the upper flow region and intensifies vortex pairs generated in the shear layer. Considering combined effects of vortex losses， frictional losses， and shock losses， the total pressure recovery coefficient and main flow coefficient reach maximum values at a throat aspect ratio of 5. The axial thrust coefficient initially increases then decreases dominated by jet deflection angles and mixing losses with ambient atmosphere. The offset ratio influences flow mixing by controlling longitudinal curvature of the nozzle. Larger offset ratio increases main flow deflection angles， intensifies compression effects on the upper tertiary flow， and strengthens spotted vortices in the shear layer. The increased vortex losses， frictional losses， and shock losses collectively reduce total pressure recovery coefficient and main flow coefficient by over 2%. Augmented jet deflection angles result in a 1.55% reduction of axial thrust coefficient.