Studying the three-dimensional hydrodynamic characteristics of opposed wall jets in a finite field through proper orthogonal decomposition and dynamic mode decomposition

In this study, to investigate the radial and vertical jet characteristics of opposed wall jets (OWJs), a three-dimensional numerical simulation is conducted using the renormalization group turbulent kinetic energy (TKE)–epsilon (RNG k–ε) turbulence model. The jet expansion rates, vortex formation, and TKE distribution patterns under varying initial water depths, nozzle spacings, and inlet velocities are studied. Additionally, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods are employed to decompose the velocity fields and extract dominant energy-containing flow structures. The results indicate that although radial and vertical jets have similar zonal structures, their associated vortices differ significantly in terms of their spatial influence. In the radial direction, the jet expansion rate decreases within the collision region and subsequently increases beyond it. In contrast, vertical jets consistently expand along the flow direction throughout their development. Furthermore, POD demonstrates superior capability to DMD in capturing coherent structures and representing the dynamic behavior of the OWJ flow field. This study enhances the understanding of energy transfer mechanisms and three-dimensional flow structures resulting from the interaction of high-speed wall jets, providing theoretical insights beneficial for controlling complex OWJ flows.