Browsing by Author "Vimalanathan K"

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    Chiral Lemniscate Formation in Magnetic Field Controlled Topological Fluid Flows
    (Wiley-VCH GmbH, 2025-04-03) Jellicoe M; Gardner Z; Alotaibi AEH; Shoemaker KE; Scott JM; Wang S; Alotaibi BM; Luo X; Chuah C; Gibson CT; He S; Vimalanathan K; Gascooke JR; Chen X; Rodger A; Huang H; Dalgarno SJ; Antunes E; Weiss GA; Li Q; Quinton JS; Raston CL
    High shear spinning top (ST) typhoon-like fluid flow in a rapidly rotating inclined tube within a vortex fluidic device (VFD) approaches homochirality throughout the liquid with toroids of bundled single-walled carbon nanotubes (SWCNTs) twisted into stable chiral lemniscates (in the shape of Figure 8s), predominantly as the R-or S-structures, for the tube rotating clockwise (CW) or counterclockwise (CCW). However, this is impacted by the Earth's magnetic field (BE). Theory predicts 1–20 MPa pressure for their formation, with their absolute chirality determined from scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. Thus, the resultant lemniscate structures establish the absolute chirality of the inner and outer components of the ST flow. These chiral flows and lemniscates can be flipped to the opposite chirality by changing the orientation of the tube relative to the inclination angle of BE, by moving the geographical location. Special conditions prevail where the tangential angle of the outer and inner flow of the ST becomes periodically aligned with BE, which respectively dramatically reduce the formation of toroids (and thus lemniscates) and formation of lemniscates from the toroids formed by the double-helical (DH) flow generated by side wall Coriolis forces and Faraday waves.
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    Sub-micron moulding topological mass transport regimes in angled vortex fluidic flow
    (The Royal Society of Chemistry, 2021-06-07) Alharbi TMD; Jellicoe M; Luo X; Vimalanathan K; Alsulami IK; Al Harbi BS; Igder A; Alrashaidi FAJ; Chen X; Stubbs KA; Chalker JM; Zhang W; Boulos RA; Jones DB; Quinton JS; Raston CL
    Shear stress in dynamic thin films, as in vortex fluidics, can be harnessed for generating non-equilibrium conditions, but the nature of the fluid flow is not understood. A rapidly rotating inclined tube in the vortex fluidic device (VFD) imparts shear stress (mechanical energy) into a thin film of liquid, depending on the physical characteristics of the liquid and rotational speed, ω, tilt angle, θ, and diameter of the tube. Through understanding that the fluid exhibits resonance behaviours from the confining boundaries of the glass surface and the meniscus that determines the liquid film thickness, we have established specific topological mass transport regimes. These topologies have been established through materials processing, as spinning top flow normal to the surface of the tube, double-helical flow across the thin film, and spicular flow, a transitional region where both effects contribute. The manifestation of mass transport patterns within the film have been observed by monitoring the mixing time, temperature profile, and film thickness against increasing rotational speed, ω. In addition, these flow patterns have unique signatures that enable the morphology of nanomaterials processed in the VFD to be predicted, for example in reversible scrolling and crumbling graphene oxide sheets. Shear-stress induced recrystallisation, crystallisation and polymerisation, at different rotational speeds, provide moulds of high-shear topologies, as 'positive' and 'negative' spicular flow behaviour. 'Molecular drilling' of holes in a thin film of polysulfone demonstrate spatial arrangement of double-helices. The grand sum of the different behavioural regimes is a general fluid flow model that accounts for all processing in the VFD at an optimal tilt angle of 45°, and provides a new concept in the fabrication of novel nanomaterials and controlling the organisation of matter.