The influence of invariant solutions on the transient behaviour of an air bubble in a Hele-Shaw channel

Keeler, Jack ORCID:, Thompson, Alice, Lemoult, Gregoire, Juel, Anne and Hazel, Andrew (2019) The influence of invariant solutions on the transient behaviour of an air bubble in a Hele-Shaw channel. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 475 (2232). ISSN 1364-5021

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We hypothesize that dynamical systems concepts used to study the transition to turbulence in shear flows are applicable to other transition phenomena in fluid mechanics. In this paper, we consider a finite air bubble that propagates within a Hele-Shaw channel containing a depth-perturbation. Recent experiments revealed that the bubble shape becomes more complex, quantified by an increasing number of transient bubble tips, with increasing flow rate. Eventually, the bubble changes topology, breaking into multiple distinct entities with non-trivial dynamics. We demonstrate that qualitatively similar behaviour to the experiments is exhibited by a previously established, depth-averaged mathematical model and arises from the model’s intricate solution structure. For the bubble volumes studied, a stable asymmetric bubble exists for all flow rates of interest, while a second stable solution branch develops above a critical flow rate and transitions between symmetric and asymmetric shapes. The region of bistability is bounded by two Hopf bifurcations on the second branch. By developing a method for a numerical weakly nonlinear stability analysis we show that unstable periodic orbits (UPOs) emanate from the first Hopf bifurcation. Moreover, as has been found in shear flows, the UPOs are edge states that influence the transient behaviour of the system.

Item Type: Article
Faculty \ School: Faculty of Science > School of Mathematics
Depositing User: LivePure Connector
Date Deposited: 06 May 2022 09:30
Last Modified: 23 Oct 2022 03:45
DOI: 10.1098/rspa.2019.0434


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