Limit cycles for the motion of finite-size particles in axisymmetric thermocapillary flows in liquid bridges

Romanò, Francesco; Kuhlmann, Hendrik C.; Ishimura, Misa; Ueno, Ichiro

doi:10.1063/1.5002135

Cited by 32 publications

(44 citation statements)

References 39 publications

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“…We stress that such a simplified particle-boundary interaction model has been proven successful at capturing the leading-order dynamics of interaction phenomena between small particles and driving boundaries (either walls or shear surfaces). This has been confirmed by comparison with fully-resolved simulations [26,27] and experiments [28]. Moreover, recent studies show that the same non-trivial physics is predicted by employing the PSI model and more physically-sound interaction forces such as the augmented Stokes drag of [6], see [14,15,29].…”

Section: Problem Formulationsupporting

confidence: 62%

“…The initial particle position is (x 0 , y 0 ) = (−0.25, 0), the Stokes number is fixed to St = 1, the particle-to-fluid density ratio is varied in the interval ∈ [0.5, 1.5] and the Strouhal number of the flow ranges in Str ∈ [0.0005, 0.1]. As shown by [26][27][28]30], ∆ is of the same order of magnitude of a, hence in the followings we set ∆ = a. All the simulations are run in dimensional form for t = 10 and Ω = 2 × 10 3 .…”

Section: Resultsmentioning

confidence: 99%

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Particle Coherent Structures in Confined Oscillatory Switching Centrifugation

Romanò

2021

Crystals

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A small spherical rigid particle in a cylindrical cavity is considered. The harmonic rotation of the cavity wall drives the background flow characterized by the Strouhal number Str, assumed as the first parameter of our investigation. The particle immersed in the flow (assumed Stokesian) has a Stokes number St=1 and a particle-to-fluid density ratio ϱ which is assumed as the second parameter of this study. Building on the theoretical understanding of the recently discovered oscillatory switching centrifugation for inertial particles in unbounded flows, we investigate the effect of a confinement. For the first time we study how the presence of a wall affects the particle trajectory in oscillatory switching centrifugation dynamics. The emergence of two qualitatively different particle attractors is characterized for particles centrifuged towards the cavity wall. The implication of two such classes of attractors is discussed focusing on the application to microfluidics. We propose some strategies for exploiting the confined oscillatory switching centrifugation for selective particle segregation and for the enhancement of particle interaction events.

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Section: Problem Formulationsupporting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Particle Coherent Structures in Confined Oscillatory Switching Centrifugation

Romanò

2021

Crystals

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“…Due to the lack of data in the literature for Pr = 68, the basic state obtained by our code for an indeformable interface has been compared by independent calculations of F. Romanò (private communication, see also Romanò et al (2017)). All results compare very well qualitatively as well as quantitatively, even though both codes differ and different grids have been used.…”

Section: Numerical Methods and Code Verificationmentioning

confidence: 99%

Stability of Thermocapillary Flow in High-Prandtl-Number Liquid Bridges Exposed to a Coaxial Gas Stream

Stojanovic

Kuhlmann

2020

Microgravity Sci. Technol.

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The stability of thermocapillary flow in a liquid bridge made from 5 cSt silicone oil (Pr = 68) is computed numerically. To improve the numerical model as compared to the standard approach, we consider the flow in the liquid bridge fully coupled to the flow in the ambient gas, temperature-dependent material parameters, and a dynamically deforming liquid-gas interface. We address the full two-phase-flow problem of interest for the space experiment JEREMI and investigate the effect of a steady axisymmetric coaxial gas flow which is imposed at the inlet of the annular gap between the liquid bridge and the outer confining cylinder. Under zero-gravity the flow is primarily driven by the imposed temperature gradient with viscous stresses from the gas phase being small. However, the heat transfer between liquid and the gas, and thus the temperature fields are strongly affected by the forced flow in the gas phase. As a result the stability of the steady axisymmetric flow depends sensitively on the flow direction and the temperature of the gas. If the temperature of the gas is identical to that of the support rod of the liquid bridge a gas stream opposing the thermocapillary stresses strongly destabilizes the basic flow. In a co-flow configuration the basic state is stabilized. Curves of neutral Reynolds numbers as functions of the strength of the annular gas flow are discussed for two aspect ratios of the liquid bridge.

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“…2017; Romanò et al. 2017). In laminar micro- or millimetric three-dimensional flows, the particle–boundary interaction may lead to non-trivial accumulation phenomena such as finite-size Lagrangian coherent structures which have been observed experimentally (Schwabe, Hintz & Frank 1996; Kuhlmann et al.…”

Section: Introductionmentioning

confidence: 99%

Stokesian motion of a spherical particle near a right corner made by tangentially moving walls

2021

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The slow motion of a small buoyant sphere near a right dihedral corner made by tangentially sliding walls is investigated. Under creeping-flow conditions the force and torque on the sphere can be decomposed into eleven elementary types of motion involving simple particle translations, particle rotations and wall movements. Force and torque balances are employed to find the velocity and rotation of the particle as functions of its location. Depending on the ratio of the wall velocities and the gravitational settling velocity of the sphere, different dynamical regimes are identified. In particular, a non-trivial line attractor/repeller for the particle motion exists at a location detached from both the walls. The existence, location and stability of the corresponding two-dimensional fixed point are studied depending on the wall velocities and the buoyancy force. The impact of the line attractors/repellers on the motion of small particles in cavities and its relevance for corner cleaning applications are discussed.

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Limit cycles for the motion of finite-size particles in axisymmetric thermocapillary flows in liquid bridges

Cited by 32 publications

References 39 publications

Particle Coherent Structures in Confined Oscillatory Switching Centrifugation

Particle Coherent Structures in Confined Oscillatory Switching Centrifugation

Stability of Thermocapillary Flow in High-Prandtl-Number Liquid Bridges Exposed to a Coaxial Gas Stream

Stokesian motion of a spherical particle near a right corner made by tangentially moving walls

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