Transition from dripping to jetting in power-law fluids

This computational study employs a finite volume method with axisymmetric coordinates and volume-of-fluid interface tracking to investigate the regime transition mechanisms from discrete droplet generation to continuous jet breakup in power-law fluid systems. Validated against experimental data, the analysis systematically examines three distinct regimes—periodic dripping (PD), dripping faucet (DF), and jetting (J)—across power-law indices from shear-thinning (n=0.6) to shear-thickening (n=1.4) fluids. The rheological properties of non-Newtonian fluids can influence the flow regime transition and breakup length. In the PD regime, shear-thinning fluids (n=0.6) exhibit satellite droplet suppression, while shear-thickening fluids (n=1.4) develop elongated neck structures that generate satellite droplets. The DF regime emerges exclusively at low Ohnesorge number (Oh), demonstrating transitional behavior between dripping and jetting modes. When Weber number (We) > 4, all fluids transition to the J regime where rheological properties critically influence breakup dynamics: shear-thickening fluids display maximum breakup lengths with distinctive beads-on-string morphology, while shear-thinning fluids achieve the shortest breakup lengths. Notably at We=3.6, both shear-thinning(n=0.6) and shear-thickening(n=1.2,1.4) fluids bypass intermediate regimes(DF) to enter the J regime directly. In the J regime, shear-thinning fluids exhibit higher satellite droplet formation frequencies, forming a thick, blunt neck profile, while shear-thickening fluids develop thin, elongated necks that fracture during retraction, producing multiple satellite droplets. The study explores the influence of rheological properties on flow state transition and satellite droplet formation, providing crucial insights for applications that demand precise control over non-Newtonian fluid breakup dynamics.