Dynamical similarity and instabilities in high-Stokes-number oscillatory flows of superfluid helium

Identifying a Superfluid Reynolds Number via Dynamical Similarity.

The Reynolds number provides a characterization of the transition to turbulent flow, with wide application in classical fluid dynamics. Identifying such a parameter in superfluid systems is challenging due to their fundamentally inviscid nature. Performing a systematic study of superfluid cylinder wakes in two dimensions, we observe dynamical similarity of the frequency of vortex shedding by a ...

Simulation of dynamical properties of normal and superfluid helium.

The formation of a superfluid when (4)He is cooled below the characteristic lambda transition temperature is accompanied by intricate quantum mechanical phenomena, including the emergence of a Bose condensate. A combination of path integral and semiclassical techniques is used to calculate the single-particle velocity autocorrelation function across the normal-to-superfluid transition. We find ...

Transient growth of perturbations in Stokes oscillatory flows

Nonlinear Second Sound Waves in superfluid helium: Instabilities, turbulence and Rogue Waves

Recent work on nonlinear second sound wave propagation and acoustic turbulence in superfluid He is reviewed. Observations of direct and inverse turbulent energy cascades are described. The direct cascade arises due to the strong nonlinear dependence of the second sound wave velocity on its amplitude. The flux of energy injected at the driving frequency is transformed via successively higher har...

Dynamical Instabilities in High-Obliquity Systems

High-inclination circumplanetary orbits that are gravitationally perturbed by the central star can undergo Kozai oscillations—large-amplitude, coupled variations in the orbital eccentricity and inclination. We first study how this effect is modified by incorporating perturbations from the planetary oblateness. Tremaine et al. (2009) found that, for planets with obliquities > 68.875, orbits in t...