Vortex Shedding from an Object Moving in Superfluid $^4$He at mK Temperatures and in a Bose-Einstein Condensate

TL;DR

This paper compares vortex shedding phenomena in superfluid helium and Bose-Einstein condensates, revealing a linear relation between shedding frequency and velocity excess above a critical threshold, with implications for understanding quantum turbulence.

Contribution

It provides a comparative analysis of vortex shedding in superfluid helium and BECs, highlighting the linear dependence of shedding frequency on velocity and the role of oscillation frequency.

Findings

Vortex shedding frequency $f_v$ depends linearly on velocity excess $\, ext{above } v_c$

Coefficient $a$ is proportional to oscillation frequency $\, ext{above } \, ext{a characteristic frequency}$

Finite shedding frequency persists as oscillation frequency approaches zero

Abstract

Vortex shedding from a microsphere oscillating in superfluid $^4$He at mK temperatures is compared with that from a laser beam moving in a Bose-Einstein condensate (BEC) as observed by other authors. In particular, in either case a linear dependence of the shedding frequency $f_v$ on $\Delta v = v - v_c$ is observed, where $v$ is the velocity amplitude of the sphere or the constant velocity of the laser beam above a critical velocity $v_c$ for the onset of turbulent flow: $f_v = a \,\Delta v$, where the coefficient $a$ is proportional to the oscillation frequency $ \omega $above some characteristic frequency $\omega_k$ and assumes a finite value for steady motion $\omega \rightarrow 0$.