Investigation of downstream mixing behavior and flow dynamics induced by dissimilar fluid injection from bluff body embedded ports

The two-dimensional unsteady laminar flow past a slotted cylinder facilitated with fluid injection is studied to examine the mixing behavior between upstream air and the fluid injected from the cylinder-slots for different slot angular positions (0°–90°). Additionally, wake dynamics and the resulting variations in key hydrodynamic quantities resulting from fluid–fluid interaction are analyzed. Simulations are primarily conducted for an injected fluid and air velocity ratio (Vr) of 1, with additional cases up to 3 to assess the impact of injection momentum. Pressure, velocity, and vorticity contours are used to analyze wake dynamics, while mass-fraction and mixture-fraction fields are examined to check mixing characteristics. Furthermore, the recurrence quantification analysis (RQA) is used to understand the underlying flow dynamics. For Vr=1, two distinct wake characteristics are identified. At low injection angles (0°–20°), the wake remains symmetric with the absence of vortex shedding, resulting in minimal lift and drag. Beyond 20°, vortex shedding emerges for all configurations. For 0°–20° cases, the flow exhibits a narrow mixing layer and high downstream mass-fraction variance, indicating weak mixing. Mixing is enhanced at higher injection angles (60°–90°), as indicated by a wider mixing layer and the lowest downstream variance. However, intensified vortex shedding for 60°–90° cases leads to stronger wake oscillations and higher hydrodynamic forces. RQA of the lift coefficient shows stable equilibrium at low injection angles, transitioning to periodic dynamics at higher angles. Despite the few dynamical variations, similar mixing and hydrodynamic trends persist for all velocity ratios considered.