Hydrodynamic Transitions with Changing Particle Size That Control Ice Lens Growth

You

et al. 2016

Sci Rep

Freezing colloidal suspensions widely exists in nature and industry. Interface instability has attracted much attention for the understandings of the pattern formation in freezing colloidal suspensions. However, the interface instability modes, the origin of the ice banding or ice lamellae, are still unclear. In-situ experimental observation of the onset of interface instability remains absent up to now. Here, by directly imaging the initial transient stage of planar interface instability in directional freezing colloidal suspensions, we proposed three interface instability modes, Mullins-Sekerka instability, global split instability and local split instability. The intrinsic mechanism of the instability modes comes from the competition of the solute boundary layer and the particle boundary layer, which only can be revealed from the initial transient stage of planar instability in directional freezing.

Section: The Origin Of the Interface Instabilitymentioning

confidence: 99%

Interface instability modes in freezing colloidal suspensions: revealed from onset of planar instability

You

et al. 2016

Sci Rep

“…The interaction of particles with a solidification front is a phenomenon encountered in numerous natural and technological situations, such as the evolution of frozen soils by frost heave or by ice lenses formation [1][2][3][4][5][6][7][8], cryobiology [9,10], food industry [11] and materials science, from alloy casting in presence of particles [12][13][14] to the fabrication of bio-inspired composites [15]. When a particle suspension freezes, a solidification front interacts with the dispersed particles by short range thermomolecular forces induced by Van der Waals like interactions [16,17].…”

Section: Introductionmentioning

confidence: 99%

Interaction of Multiple Particles with a Solidification Front: From Compacted Particle Layer to Particle Trapping

et al. 2017

The interaction of solidification fronts with objects such as particles, droplets, cells, or bubbles is a phenomenon with many natural and technological occurrences. For an object facing the front, it may yield various fates, from trapping to rejection, with large implications regarding the solidification pattern. However, whereas most situations involve multiple particles interacting with each other and the front, attention has focused almost exclusively on the interaction of a single, isolated object with the front. Here we address experimentally the interaction of multiple particles with a solidification front by performing solidification experiments of a monodisperse particle suspension in a Hele-Shaw cell with precise control of growth conditions and real-time visualization. We evidence the growth of a particle layer ahead of the front at a close-packing volume fraction, and we document its steady-state value at various solidification velocities. We then extend single-particle models to the situation of multiple particles by taking into account the additional force induced on an entering particle by viscous friction in the compacted particle layer. By a force balance model this provides an indirect measure of the repelling mean thermomolecular pressure over a particle entering the front. The presence of multiple particles is found to increase it following a reduction of the thickness of the thin liquid film that separates particles and front. We anticipate the findings reported here to provide a relevant basis to understand many complex solidification situations in geophysics, engineering, biology, or food engineering, where multiple objects interact with the front and control the resulting solidification patterns.

“…= dp dz (9) where ∆σ p yz = σ p yz (x, e/2, z) − σ p yz (x, −e/2, z)]. The symmetry σ p yz (x, e/2, z) = −σ p yz (x, −e/2, z) and the boundary conditions (8) give :…”

Section: Janssen Effectmentioning

confidence: 99%

“…The solidification of a suspension (i.e. of a two phase mixture involving solid particles dispersed in a fluid) arises in a number of situations either natural as the freezing of soils [1][2][3][4][5][6][7][8] or man-made as in the food industry 9 , the casting of particle rich alloys [10][11][12] or the making of bio-inspired composite materials 13 . Its physics involves phenomena referring either to solidification, to suspension, or to the interaction between a solidification front and the suspension particles.…”

Section: Introductionmentioning

confidence: 99%

Wall friction and Janssen effect in the solidification of suspensions

et al. 2018

We address the mechanical effect of rigid boundaries on freezing suspensions. For this we perform the directional solidification of monodispersed suspensions in thin samples and we document the thickness h of the dense particle layer that builds up at the solidification front. We evidence a change of regime in the evolution of h with the solidification velocity V with, at large velocity, an inverse proportionality and, at low velocity, a much weaker trend. By modelling the force balance in the critical state for particle trapping and the dissipation phenomena in the whole layer, we link the former evolution to viscous dissipation and the latter evolution to solid friction at the rigid sample plates. Solid friction is shown to induce an analog of the Janssen effect on the whole layer. We determine its dependence on the friction coefficient between particles and plates, on the Janssen's redirection coefficient in the particle layer, and on the sample depth. Fits of the resulting relationship to data confirm its relevance at all sample depths and provide quantitative determinations of the main parameters, especially the Janssen's characteristic length and the transition thickness h between the above regimes. Altogether, this study thus clarifies the mechanical implication of boundaries on freezing suspensions and, on a general viewpoint, provides a bridge between the issues of freezing suspensions and of granular materials.