Breakup, three-stage velocity and internal flow structures of low-Weber-number liquid-metal jets under transverse magnetic fields

Using three-dimensional direct numerical simulations, this study investigates breakup and internal flows of liquid-metal jets in the dripping regime (We=1.695) under transverse magnetic fields (0≤Ha≤360). Increasing Ha enhances stability. Morphology turns from asymmetric at Ha=0 to uniform at Ha≥180. Breakup length remains stable at Ha=180 but grows with breakup events at Ha=288 and 360. Centerline velocity transitions from a two-stage to a three-stage pattern between 180<Ha<288: two-stage for Ha≤180, three-stage for Ha≥288. In Segment I, velocity decreases linearly with deceleration rising as Ha increases. For Ha≥288, Segment III shows linear velocity increase with expanding coverage but declining growth rate. For the two Ha≥288 cases, Segment I's deceleration zone uniformly extends to x*=0.65. Internal flow reveals progressive longitudinalization of the velocity core, with transverse gradients nearly vanishing at Ha=360. Lorentz-force momentum confinement homogenizes velocity and lengthens the jet. Since only discrete Ha values are simulated, the exact transition threshold is bracketed within 180<Ha<288. These results support magnetic regulation of liquid-metal jets for fusion devices. Future work will refine sampling between 180 and 288 and extend to higher Ha and varied We.