Coating with deformable rolls: An experimental investigation of the ribbing instability

Chong, Yang; Gaskell, Philip; Kapur, Nikil

doi:10.1016/j.ces.2007.04.029

Cited by 15 publications

(11 citation statements)

References 18 publications

(17 reference statements)

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“…In the case of a bi-layer coating, the two flui ds are mixed together under the vortex action at the contact output. Chong et al (2007) observed that ribbing is present over a wide range of operating parameters for negative gaps. We can thus consider that ribbing and vortex occur during swallowing and that the food bolus is therefore mixed with the saliva film.…”

Section: Application To Swallowingmentioning

confidence: 98%

A biomechanical model of swallowing for understanding the influence of saliva and food bolus viscosity on flavor release

Loubens

Magnin

Doyennette

et al. 2011

Journal of Theoretical Biology

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After swallowing a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The objective of the present article was to understand and quantify physical mechanisms explaining pharyngeal mucosa coating. An elastohydrodynamic model of swallowing was developed for Newtonian liquids that focused on the most occluded region of the pharyngeal peristaltic wave. The model took lubrication by saliva film and mucosa deformability into account. Food bolus flow rate and generated load were predicted as functions of three dimensionless variables: the dimensionless saliva flow rate, the viscosity ratio between saliva and the food bolus, and the elasticity number. Considering physiological conditions, the results were applied to predict aroma release kinetics. Two sets of conditions were distinguished. The first one was obtained when the saliva film is thin, in which case food bolus viscosity has a strong impact on mucosa coating and on flavor release. More importantly, we demonstrated the existence of a second set of conditions. It was obtained when the saliva film is thick and the food bolus coating the mucosa is very diluted by saliva during the swallowing process and the impact of its viscosity on flavor release is weak. This last phenomenon explains physically in vivo observations for Newtonian food products found in the literature. Moreover, in this case, the predicted thickness of the mix of food bolus with saliva coating the mucosa is approximately of 20 μm; value in agreement with orders of magnitude found in the literature.

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Section: Application To Swallowingmentioning

confidence: 98%

A biomechanical model of swallowing for understanding the influence of saliva and food bolus viscosity on flavor release

Loubens

Magnin

Doyennette

et al. 2011

Journal of Theoretical Biology

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“…Similar interactions between compliant boundaries and lubrication flows also arise in a variety of natural processes including pulmonary airways reopening (Jensen et al 2002;Grotberg & Jensen 2004;Heap & Juel 2008;Heil & Hazel 2011) and the spreading of magma underneath deforming strata (Bunger & Cruden 2011;Michaut 2011;Lister, Peng & Neufeld 2013), as well as industrial application, such as roll coating (Carvalho & Scriven 1997Chong, Gaskell & Kapur 2007) and fabrication of MEMS (Hosoi & Mahadevan 2004).…”

Section: Introductionmentioning

confidence: 97%

Modelling the suppression of viscous fingering in elastic-walled Hele-Shaw cells

et al. 2013

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Recent experiments by Pihler-Puzovic et al. (Phys. Rev. Lett., vol. 108, 2012, article 074502) have shown that the onset of viscous fingering in circular Hele-Shaw cells in which an air bubble displaces a viscous fluid is delayed considerably when the top boundary of the cell is replaced by an elastic membrane. Non-axisymmetric instabilities are only observed at much larger flow rates, and the large-amplitude fingers that develop are fundamentally different from the highly branched fingers in rigid-walled cells. We explain the mechanism for the suppression of the instability using a combination of linear stability analysis and direct numerical simulations, based on a theoretical model that couples a depth-averaged lubrication equation for the fluid flow to the Föppl-von Kármán equations, which describe the deformation of the elastic membrane. We show that fluid-structure interaction affects the instability primarily via two changes to the axisymmetric base flow: the axisymmetric inflation of the membrane prior to the onset of any instabilities slows down the expansion of the air bubble and forces the air-liquid interface to propagate into a converging fluid-filled gap. Both of these changes reduce the destabilizing viscous effects that drive the fingering instability in a rigid-walled cell. In contrast, capillary effects only play a very minor role in the suppression of the instability.

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“…The challenge of scalable manufacturing of microtrench structures has motivated the authors to look more into a common roll-to-roll manufacturing defect known as ribbing (Figure S1, Supporting Information), where spatially periodic patterns appear transverse to the roll-coating direction. [32][33][34][35] During the roll-coating process, a positive pressure gradient is developed in the downstream meniscus of the coating fluid. [36] The flow becomes unstable when the pressure gradient exceeds a critical value, and a finger-like growth is observed.…”

Section: Introductionmentioning

confidence: 99%

“…The ribbing behavior of Newtonian and non-Newtonian fluids has been studied through experimental and computational models to minimize roll-coating defects. [32][33][34][35]45] It was found that the ribbing periodicity or wavelength (λ Ribbing ) and amplitude have a strong relationship with material properties as well as process parameters, including the surface energy γ, viscosity η, roller radius R, roller gap d, and roller speed U. [37,38,46,47] For a Newtonian fluid, the onset condition of the ribbing instability was found describable by two dimensionless parameters: the capillary number Ca = η*U/γ and the geometric factor R/d.…”

Section: Introductionmentioning

confidence: 99%

“…The critical capillary number Ca* showed a linear proportionality with the geometric factor R/d for Newtonian fluids. [32,33,35,38,48,49] On the other hand, the critical Capillary number for non-Newtonian fluids is much lower than for Newtonian fluids. [49] However, unlike the Newtonian fluid, the theoretical prediction of the Ca* in the viscoelastic fluid is not obtainable.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Template‐Free Scalable Fabrication of Linearly Periodic Microstructures by Controlling Ribbing Defects Phenomenon in Forward Roll Coating for Multifunctional Applications

Islam

Perera

Black

et al. 2022

Adv Materials Inter

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developing multifunctional surfaces with unique capabilities, including superhydrophobicity, [1,2] self-cleaning, [3,4] anti-icing, [3,5] anti-biofoulin, [6,7] biological sensors, [6] and radiative cooling. [6,8] For example, Namib Desert beetles use the superhydrophobicsuperhydrophilic micropatterned skin to harvest water from fog. [12][13][14] Plants such as lotus utilize microstructures on leaves to influence wetting behavior and enable self-cleaning. [12,15] Sharks' unique skin morphology augments the near-wall vorticity during turbulent flow. This augmentation reduces the skin friction and enables sharks to be one of the most efficient swimming species in the ocean. [16][17][18] These dragreducing microstructures are particularly interesting to the scientific community. Thus, researchers have focused on periodic microstructures aligned in the flow direction, similar to sharkskin. [19] In prior modeling and experimentation, researchers have decreased frictional drag by using different variations of linear periodic microstructures. For example, Xu et al. developed a series of linear microtrenches demonstrating a maximum drag reduction of ≈30% in high Reynolds number applications. [20] In addition, Park et al. studied the impact of grating parameters on drag reduction and demonstrated a max drag reduction of 75%. [21] Lithography is one of the standard processes for manufacturing superhydrophobic periodic microstructures. [20][21][22] Periodic micro/nanoscale structures from nature have inspired the scientific community to adopt surface design for various applications, including superhydrophobic drag reduction. One primary concern of practical applications of such periodic microstructures remains the scalability of conventional microfabrication technologies. This study demonstrates a simple template-free scalable manufacturing technique to fabricate periodic microstructures by controlling the ribbing defects in the forward roll coating. Viscoelastic composite coating materials are designed for roll-coating using carbon nanotubes (CNT) and polydimethylsiloxane (PDMS), which helps achieve a controllable ribbing with a periodicity of 114-700 µm. Depending on the process parameters, the patterned microstructures transition from the linear alignment to a random structure. The periodic microstructure enables hydrophobicity as the water contact angles of the samples ranged from 128° to 158°. When towed in a static water pool, a model boat coated with the microstructure film shows 7%-8% faster speed than the boat with a flat PDMS film. The CNT addition shows both mechanical and electrical properties improvement. In a mechanical scratch test, the cohesive failure of the CNT-PDMS film occurs in ≈90% higher force than bare PDMS. Moreover, the nonconductive bare PDMS shows sheet resistance of 747.84-22.66 Ω □ −1 with 0.5 to 2.5 wt% CNT inclusion.

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Coating with deformable rolls: An experimental investigation of the ribbing instability

Cited by 15 publications

References 18 publications

A biomechanical model of swallowing for understanding the influence of saliva and food bolus viscosity on flavor release

A biomechanical model of swallowing for understanding the influence of saliva and food bolus viscosity on flavor release

Modelling the suppression of viscous fingering in elastic-walled Hele-Shaw cells

Template‐Free Scalable Fabrication of Linearly Periodic Microstructures by Controlling Ribbing Defects Phenomenon in Forward Roll Coating for Multifunctional Applications

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