Twin inclined jets in crossflow: experimental investigation of different flow regimes and jet elevations

The present experimental study is dedicated to unfolding the mixing process generated by double-inclined, variably elevated jets in crossflow. Twin tandem jets in crossflow are very common in the industry and are closely dependent on several parameters. Detailing the induced interactions in such a model would ultimately enhance our understanding and help optimize related applications. The jets handled in the present work are placed three diameters apart, arranged in line with the oncoming crossflow and sent at variable levels (h = 0, 1, 2, 5 cm) from the ground of a wind tunnel and are discharged from elliptic discharging cross sections. Elliptic jets are of particular interest in applications like industrial and boat chimneys, and are practically easily obtained by razing circular cylinders at the desired inclination and height. Particle image velocimetry and coupled charge device CCD camera were used. The dynamic and turbulent behavior of the resulting flowfield was characterized in terms of streamlines, velocity components and vortical structures. The obtained data helped highlight the impact of jets’ elevation over their mixing mechanism among the surrounding free stream: establishment of the resulting flowfield dynamics and settlement of the induced vortical structures. The mixing process evolution was also considered under different flow regimes. For the matter an injection ratio (defined as jets to the mainstream’s velocity ratio) raging between 0.67, 1 and 1.29 was considered. These cases correspond to jets dynamically dominated by, equivalent to or more dominant than the mainstream. The impact of jets’ elevation combined to that of the injection ratio affects both the developed vortical structures and the established dynamic fields, which in turn highly affects the induced mixing process.