Thermal Convection and Temperature Inhomogeneity in a Vibrofluidized Granular Bed: The Influence of Sidewall Dissipation

Windows-Yule, Kit; Rivas, Nicolas; Parker, D.J.

doi:10.1103/physrevlett.111.038001

Cited by 39 publications

(36 citation statements)

References 25 publications

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“…A further confirmation that BBD-TC is essentially a "bulk" effect comes from simulations [15] and theory [21,22] where lateral walls are not required to observe it. Convective circulation in granular gases has been seen also in experiments, where lateral walls are always inelastic [23][24][25][26], and successive simulations with elastic [27] and also inelastic walls [28].The role of lateral walls in dilute granular convection has not been fully understood yet. Some of the mentioned studies recognize that lateral walls influence the observations.…”

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confidence: 99%

Thermal Convection in Granular Gases with Dissipative Lateral Walls

et al. 2016

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We consider a granular gas under the action of gravity, fluidized by a vibrating base. We show that a horizontal temperature gradient, here induced by limiting dissipative lateral walls (DLW), leads always to a granular thermal convection (DLW-TC) that is essentially different from ordinary bulk-buoyancy-driven convection (BBD-TC). In an experiment where BBD-TC is inhibited, by reducing gravity with an inclined plane, we always observe a DLW-TC cell next to each lateral wall. Such a cell squeezes towards the nearest wall as the gravity and/or the number of grains increase. Molecular dynamics simulations reproduce the experimental results and indicate that at large gravity or number of grains the DLW-TC is barely detectable.Shaken granular media escape most of the laws of equilibrium thermodynamics and statistical mechanics [1], ranging from slow plastic flows [2] to fast gas-like dynamics [3][4][5]. In the wide granular phenomenology [6], an ubiquitous pattern is the convective cell. Notwithstanding its widespread occurrence, many different mechanisms lead to granular convection, and their relevance depends on the granular state under scrutiny.At high packing fraction and low fluidization, "dense convection" is observed [7][8][9][10]. A convincing explanation of dense convection comes from the asymmetric tangential friction at the lateral walls that results in a net downward shear force [11][12][13]. Dense granular convection can also involve more complex mechanisms, including the formation of unstable heaps at the free surface [14].In highly fluidized states (granular gases), the only known theoretical mechanism is bulk buoyancy-driven thermal convection (BBD-TC), first observed in simulations [15,16]. In analogy to molecular liquids [17,18], it originates from the buoyancy force associated to temperature/density gradients that, because of the intrinsic bulk inelasticity, emerge spontaneously [19], even with an open or reflecting top boundary [20]. BBD-TC is an instability of the hydrostatic state which requires a combination of parameters (including inelasticity, gravity and dimensions) to overcome a certain threshold [21,22]. A further confirmation that BBD-TC is essentially a "bulk" effect comes from simulations [15] and theory [21,22] where lateral walls are not required to observe it. Convective circulation in granular gases has been seen also in experiments, where lateral walls are always inelastic [23][24][25][26], and successive simulations with elastic [27] and also inelastic walls [28].The role of lateral walls in dilute granular convection has not been fully understood yet. Some of the mentioned studies recognize that lateral walls influence the observations. For instance, a downward flow velocity is always observed near lateral walls, perhaps because of a reduced buoyancy originated from enhanced dissipation [15,23,28]. However, quite contrasting results emerge in simulations and experiments concerning the necessity of dissipation at the lateral walls. In some simulations convection is strong even w...

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Thermal Convection in Granular Gases with Dissipative Lateral Walls

et al. 2016

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“…The existence of convection can raise segregation patterns. Segregation can be controlled by altering the convection strength [109] . C.R.K Windows-Yule et al [110] investigated the influence of convection on segregation in a binary system and determine that segregation rate increased with convection intensity.…”

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Convection, Segregation and Pattern Formation in Horizontally Vibrated Granular Materials

Rehman¹

2017

ijetst

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We reviewed the developments in segregation, convection and pattern formation in horizontally vibrated granular systems which are important for the improvement of several industrial developments, such as agriculture, mining, pharmaceutical, geo-sciences, civil engineering etc. The most of previous theoretical and experimental research works were focused on vertical vibration direction; only limited studies explored the horizontally vibrated granular systems. Segregation, convection and pattern formation in horizontally vibrated systems are complex phenomena. Size ratio, particle properties, energy input, vibrational direction and boundary conditions are all playing significant roles. Several studies have been performed but extensive experiments and theoretical models are still mandatory to attain the firm explanations of these phenomena. Progresses in simulation software, novel analytical models and innovative experimental methods are desirable to sustain developments on these issues.

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“…Dissipative walls are set with the same restitution coefficient as between particles, r w = 0.9. The effects of dissipative walls on convective states have already been studied in similar setups, both experimentally and numerically [119]. Here we are interested in the effects of walls on the excitation or suppression of the modes relevant in the transition.…”

Section: System and Simulationsmentioning

confidence: 99%

“…Eliminating friction completely quantitatively modifies the phase space, but all studied states were still observed. We remark that the role of friction and dissipation in analogous experiments is a matter of ongoing research [119]. We now introduce dimensionless variables, which will be used for the rest of the text.…”

Section: Simulationsmentioning

confidence: 99%

“…In addition to our confirmation of previous theoretical and simulational results, presented in the previous chapter, we also report the observation of two new phenomena which are, to the best of the authors' knowledge, previously unobserved either in experimental or simulated granular systems. The role of dissipation at the horizontal boundaries of the system is also explored; sidewalls have previously been shown to significantly affect the behaviour of both two- [124] and three-dimensional [119] systems, and as such are likely to have a significant impact on the phenomena observed in the quasi-one-dimensional (quasi-1D) and laterally constrained three-dimensional systems such as those used here.…”

Section: Introductionmentioning

confidence: 99%

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Discrete and continuum descriptions of shaken granular matter

Rivas¹

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Thermal Convection and Temperature Inhomogeneity in a Vibrofluidized Granular Bed: The Influence of Sidewall Dissipation

Cited by 39 publications

References 25 publications

Thermal Convection in Granular Gases with Dissipative Lateral Walls

Thermal Convection in Granular Gases with Dissipative Lateral Walls

Convection, Segregation and Pattern Formation in Horizontally Vibrated Granular Materials

Discrete and continuum descriptions of shaken granular matter

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