How obstructed jets experience detrainment

A comprehensive understanding of turbulent jets discharged into obstructed environments remains a critical gap in the current literature. This issue holds significant importance for applications ranging from environmental fluid dynamics to industrial processes. The primary goal of this study is to theoretically investigate the dynamics of planar turbulent non-buoyant jets interacting with arrays of rigid obstacles, supported by a comparison between theoretical predictions and experimental data. Specifically, our analysis focuses on the entrainment process, revealing that obstructions in non-stratified flows impede entrainment, reversing it into detrainment. This finding is novel because (i) detrainment in natural settings is typically associated with buoyancy-driven flows, such as plumes or density currents in stratified environments, and (ii) to the best of the authors' knowledge, this is the first validation of theoretical entrainment coefficients with experimental data for obstructed non-buoyant jets. Experiments were conducted with turbulent non-buoyant jets using particle image velocimetry, providing detailed insights into flow structure and entrainment dynamics. Furthermore, the study explores jet particle dispersion and diffusivity through a Lagrangian framework. The results demonstrate significant differences in dispersion behavior between unobstructed and obstructed jets, showing that obstacle-induced blockage profoundly influences flow characteristics and jet detrainment. In particular, obstructions play a fundamental role, initially affecting the dispersion mechanism through obstacle diameter and later through the free spacing between obstacles. These findings provide valuable contributions to understanding flow physics in complex environments and have implications for engineering and environmental applications.