Bianca-Ioana Constandache; Megan Dransfield

Lancaster University (Bailrigg, UK) | | Degree: BC: MPhys Theoretical Physics (Hons) / MD: MPhys Physics (Hons)
An investigation of non-linear behaviour of micromechanical oscillators in quantum fluids

Abstract

As technological advances progress, new developments from optoelectronics to microchips or high-accuracy detectors encounter the unavoidable problem of turbulence. To understand this behaviour, the phenomenon needs to be studied from the simplest systems so that it can be precisely modelled, ensuring a stable foundation for further developments. In this project, we investigate the behaviour of a mechanical resonating wire submerged in liquid Helium-4 and study the effect of quantum turbulence in quantum fluids at superfluid temperatures. Minimising the viscosity of the working fluid uncovered the clear transition from the laminar to the turbulent regime, therefore providing information about the critical velocity. This study experimented with various theoretical models, using linear and non-linear Lorentzian fitting to the linearly damped simple harmonic oscillator and Duffing oscillator model, providing insights into factors such as resonant frequency, damping and their dependence on temperature. The results indicate that at higher driving forces the models tested were no longer suitable and therefore terms should be added to take into account the contributions of factors such as backflow, normal to superfluid fraction and other non-linearities related to the formation of quantum vortices.

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Bianca-Ioana Constandache; Megan Dransfield