Similarity solutions for capillary pinch-off in fluids of differing viscosity

Self-similar profiles associated with capillary instability of a fluid thre ad of viscosity lambda eta in surrounding fluid of viscosity eta are obtain ed for 1/16 less than or equal to lambda less than or equal to 16 via a sim plified numerical scheme. Universal similarity scaling is preserved despite an asymptotically large velocity in the pinching neck driven by nonlocal d ynamics. The numerical results agree well with experimental measurements by Cohen et al. [preceding Letter, Phys. Rev. Lett. 83, 1147 (1999)]. For all lambda, the self-similar profile is asymmetric and conical far from the mi nimum. The steep cone slope increases monotonically with lambda; the shallo w cone slope is maximized around lambda = 1/4.