Jet breakup in superfluid and normal liquid He4

Abstract

Past studies have shown that liquid jet breakup behavior can be classified into five regimes: Rayleigh, first wind, sinuous, second wind, and atomization. By experimentally examining the breakup of superfluid and normal liquid 4 He in an atmosphere of its own vapor, we investigate the evolution of the jet behavior over a large range of the traditional three-dimensional parameter space of the Ohnesorge number [Oh l ∼ O(10 −5-10 −2)], Reynolds number [Re l ∼ O(10 2-10 6)], and gas-liquid density ratio [ρ g /ρ l ∼ O(10 −4-1)]. Using dimensional analysis we find that the transition from Rayleigh to first-wind breakup occurs at a constant liquid Weber number, and that the transitions from first wind to sinuous, and sinuous to second wind occur at constant gas Weber numbers. The proposed transitions, which differ from some previous studies, are well supported by our new experimental data that extend over all three dimensions of the parameter space. We do not observe any obvious effects of superfluidity on the breakup behavior. In addition, we examine the breakup length and comment on the transition of a liquid jet to a gaseous jet as the temperature passes through the critical point.

Nanoscopic jets and filaments of superfluid He-4 at zero temperature: a DFT study

“…39 It has been pointed out that no obvious effects due to superfluidity have been observed on the breakup behavior of a liquid He jet. 14 Yet, Kolatzki et al 16 have found that He droplets undergo shape oscillations that persist for much longer times than in the case of viscous drops, a signature of the superfluid character of these droplets.…”

“…As with classical fluids, He jet breaking may lead not only to droplets but also to filaments, as observed in experiments. [14][15][16] We model here these filaments as cylinders of radius R 0 delimited by two hemispherical caps 19 and study, using the He-TDDFT approach, their contraction due to the effect of the surface tension for different values of the aspect ratio Γ = L/R 0 , 18 where L is the half-length of the filament from end-to-end. The configuration from which the real-time dynamics is initiated is a free-standing ideal filament (i.e.…”

“…This unique fluid allows for a large variation of non-dimensional parameters related to the fluid viscosity and the velocity at which it exits the nozzle, which characterize its dynamical properties. 14 This understanding has also a primary application, namely to make available helium drops with the size and velocity required by the experiments, together with size and velocity distributions as narrow as possible. This has led to recent experimental studies on the disintegration of liquid helium jets.…”

“…We notice that liquid 4 He filaments are regularly found in the experiments. [14][15][16] Liquid jets and filaments and their dynamical instabilities are well established subjects of study in classical fluids dynamics because of practical questions and applications on the one hand, and because jet dynamics probes many physical properties and theoretical approaches on the other hand, see e.g. Refs.…”

Nanoscopic jets and filaments of superfluid 4He at zero temperature: A DFT study

“…This unique fluid allows for a large variation of non-dimensional parameters related to the fluid viscosity and the velocity at which it exits the nozzle, which characterize its dynamical properties. 14 This understanding also has a primary application, namely to make available 4 He drops with the size and velocity required by the experiments, together with size and velocity distributions as narrow as possible. This has led to recent experimental studies on the disintegration of liquid 4 He jets.…”