Numerical study on the near-field characteristics of two-phase viscoelastic turbulent jets

Turbulent jets of viscoelastic fluids injected into quiescent air exhibit a distinct rod-like structure with less spray formation, which differs significantly from the fragmented appearance of Newtonian jets. To clarify the role of fluid elasticity in interfacial dynamics, this study employs numerical simulations to investigate the near-field region of viscoelastic jets issuing from a cylindrical nozzle into quiescent air. The rheological behavior of the viscoelastic fluid is captured by the Giesekus constitutive model, and numerical solutions are obtained using the rheoInterFoam solver over a range of Weissenberg numbers (Wi), inlet velocity fluctuations (s), and the tube lengths (L/D). Results indicate that in the absence of an upstream flow confinement (L/D = 0), fluid elasticity without upstream flow fails to suppress the instability and fragmentation of the jet column; in contrast, a significant reduction in the inlet velocity fluctuation markedly enhances jet stability. Further analysis of cases with upstream flow confinement (L/D ≠ 0) reveals that the distinct appearance of viscoelastic turbulent jets arises primarily from drag reduction in the wall-bounded upstream flow, rather than from fluid elasticity itself.