Fractal characteristics of the interaction between supersonic flow and dual jets

Abstract Fractal dimensions serve as a metric for evaluating the complexity of turbulent structures, thereby inferring the mixing efficiency of the jet and the mainstream. In this paper, the flow field structures of the interaction between supersonic flow and dual jets were obtained by the nanoparticle-based planar laser scattering (NPLS) technique with high spatiotemporal resolution. Based on the NPLS images, the fractal analysis was conducted. The Canny edge detection algorithm was utilized to delineate turbulent interfaces, and five subregions were defined to investigate the mixing efficiency at different streamwise positions. The results indicate that the 2D average fractal dimension of the entire interaction flow field ranges from 1.4 to 1.61. The larger orifice spacing and greater distance of the dual orifices from the leading edge of the plate, the higher the fractal dimensions. Consequently, it could be inferred that positioning the dual orifices further downstream with greater orifice spacing effectively enhances the mixing efficiency in the interactional flow. Furthermore, the analysis of streamwise subregional fractal dimensions reveals that the interaction between the dual jets and the supersonic mainstream exhibits an “increasing and decreasing” tendency in mixing efficiency along the streamwise direction.