Controlled symmetry breaking and vortex dynamics in intersecting flows

Amy Q. Shen,Noa Burshtein,Simon J. Haward

doi:10.1063/1.5087732

Amy Q. Shen, Noa Burshtein + Show 1 more

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https://doi.org/10.1063/1.5087732

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Abstract

Vortices are a ubiquitous feature in complex flows and turbulence, but their dynamics are challenging to study due to their typically transient nature. Here, we perform a detailed study of the vortex dynamics and interactions associated with a symmetry-breaking flow instability at a 4-way intersection. By precisely controlling the flow rate (hence the Reynolds number, Re) of the flow about a critical value, we are able to induce the merging of two co-rotating vortices into a single structure and similarly to induce a single vortex to split into two. Using quantitative flow velocimetry, both processes are recorded with high spatial and temporal resolution. We find that both the merging and the splitting of vortices are exponential processes, with a rate that depends on the imposed Re. The vortex dynamics in our system are intimately connected with the symmetry-breaking transition and are affected by the degree of vortex confinement, which we control by varying the aspect ratio (α) of the flow geometry. We show how the confinement affects the fundamental nature of the flow transition, which varies from super through subcritical as α is increased. Our results are of direct relevance to understanding and predicting flow transitions and vortex dynamics in flow intersections, particularly in confined environments such as in microfluidic (lab-on-a-chip) devices and in the circulatory system, and may be relevant to the prediction of vortex interactions in general.

Highlights

Swirling flows and formation of vortices have been attracting scientific attention for centuries due to their intriguing nature and prevalence in diverse environments
Vortices are commonly generated in inviscid environments such as superfluids and electro-magnetic fields. The dynamics of these vortices resembles two dimensional ideal flows,18–20 and they are often analyzed with classical fluid dynamics tools
We have examined the vortex dynamics associated with a symmetry breaking flow instability that occurs beyond a critical Reynolds number in a 4-way intersecting flow

Summary

Introduction

Swirling flows and formation of vortices have been attracting scientific attention for centuries due to their intriguing nature and prevalence in diverse environments. Even in relatively viscous flows such as in pipes and channels with small length scales, vortices can play a significant role in the fluid dynamics, at flow intersections such as T-, Y-, and X-junctions or around bends.. Even in relatively viscous flows such as in pipes and channels with small length scales, vortices can play a significant role in the fluid dynamics, at flow intersections such as T-, Y-, and X-junctions or around bends.8–17 Such configurations are common features in all flow loops including biological circulation systems. Vortices are commonly generated in inviscid environments such as superfluids and electro-magnetic fields. The dynamics of these vortices resembles two dimensional ideal flows, and they are often analyzed with classical fluid dynamics tools.

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