Two‐phase flow in a gas‐injected capillary tube

Park, Chanseok; Baek, Sang-Youp; Lee, Ki-Jun; Kim, Seong-Woo

doi:10.1002/adv.10059

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…These results highlight that the deposition of YSF on the wall of the channel is governed by Bi −1 . On the one hand, for Bi −1 > 1, the YSF is fluidized and the thickness of the deposited film increases with the velocity as observed recently in different geometries 26,33,36,37,46 . This efficient deposition process induces the rapid thinning of the plugs separating adjacent bubbles leading to their collapse.…”

Section: Bubble Production In Ysfsupporting

confidence: 61%

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

et al. 2016

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International audienceWe investigate experimentally the stability of bubble production in yield-stress fluids (YSF) and highly viscous silicone oil, using flow-focusing and T-junction devices. When the exit channel is initially pre-filled with the fluid and the gas is pressure-driven, the production is highly unstable, despite a regular frequency of bubble production in the junction. As observed for pressure-driven bubble trains in Newtonian fluids, we report that two mechanisms can explain these observations : (i) drastic reduction of the hydrodynamic pressure drop along the channel during the transient bubble production, which induces a rapid increase of the gas flow rate and (ii) thin film deposition resulting in a cascade of plug break-up and bubbles coalescence. While the drastic reduction of the pressure drop is inevitable in such two-phase flows, we show that modifying the surfaces of the channel can help stabilizing the system when the continuous phase is a YSF. To do so, we measure the thickness of the film deposited on the channel wall for rough and smooth channels. Our results are rationalized by introducing the inverse of the Bingham number Bi −1 comparing the viscous stress to the yield stress. For Bi −1 ≥ 1, a fast fluidization process associated to efficient deposition of YSF on the channel wall leads to a rapid destabilization of the bubble production. However, for Bi −1 < 1, the deposition driven by capillarity can be hindered by the wall-slip induced by the existence of the yield stress: the thickness of the deposited film is very thin and corresponds to the equivalent roughness of the channels. It is typically 40 µm thick for rough surfaces and below the limit of resolution of our setup for smooth surfaces. In this regime of Bi −1 and for smooth surfaces, the length of the plugs barely vanishes, thus the start-up flow is less prone to destabilization. These results therefore potentially open routes to steady production of aerated YSF on smooth channels in the regime of small Bi −1

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Section: Bubble Production In Ysfsupporting

confidence: 61%

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

et al. 2016

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“…In this regime, h is supposed to depend only on the ratio of the yield stress to the capillary pressure whatever the geometry (plate, fibre, channel) as highlighted by equation 4.3 and 4.7. Thus, in figure 4, we compare equation 4.7 in the limit of V → 0 to the normalized value of the first experimentally measurable value of h for (i) Carbopol gels (τ y = 70 Pa) in tubes (235 µm < R < 702 µm) (our data) (ii) Suspensions (0.2 Pa < τ y <1.5 Pa) in tubes (R = 1.93 mm) (Park et al 2003) and (iii) Carbopol gels (8 Pa < τ y < 82 Pa) on plates using T ρg as characteristic length (Maillard et al 2014) as a function of B. All data collapse on a single curve that saturates toward h/L d ∼ 0.07 when B → 0, increases like B 2 for 0.3 < B < 1 (as given by equation 4.3) and saturates again toward 1 for B > 1.…”

Section: Model and Discussionmentioning

confidence: 99%

“…In a circular channel, the deposition of YSFs has received relatively little consideration to date, despite its relevance in numerous and diverse applications in industry (e.g. gas-assisted injection molding (Park et al 2003), channel-cleaning processes in petroleum or food industry, displacement of hydraulic fracturing fluid (Boronin et al 2015)) or in biomedical research (reopening of pulmonary airways (Zamankhan et al 2012)). In this confined geometry, the capillary pressure, set by the channel's curvature typically of 10 4 m −1 , competes with the gravity and yield stresses as in the geometry of the fiber.…”

Section: Introductionmentioning

confidence: 99%

Yield-stress fluid deposition in circular channels

et al. 2017

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Since the pioneering works of Taylor and Bretherton, the thickness h of the film deposited behind a long bubble invading a Newtonian fluid is known to increase with the Capillary number power 2/3 (h ∼ RCa 2/3 ), where R is the radius of the circular tube and the Capillary number, Ca, comparing the viscous and capillary effects. This law, known as Bretherton law, is only valid in the limit of Ca < 0, 01 and negligible inertia and gravity. We revisit this classical problem when the fluid is a Yield-Stress Fluid (YSF) exhibiting both a yield stress and a shear-thinning behaviour. First, we provide quantitative measurement of the thickness of the deposited layer for Carbopol HerschelBulkley fluid in the limit where the yield-stress is of similar order of magnitude as the capillary pressure and for 0.1 < Ca < 1. To understand our observation, we use scaling arguments to extend the analytical expression of Bretherton's law to YSF in circular tubes. In the limit of Ca < 0, 1, our scaling law, in which the adjustable parameters are set using previous results concerning non-Newtonian fluid, successfully retrieves several features of the literature. First, it shows that (i) the thickness deposited behind a Bingham YSF (exhibiting a yield stress only) is larger than for a Newtonian fluid and (ii) the deposited layer increases with the amplitude of the yield stress. This is in quantitative agreement with previous numerical results concerning Bingham fluid. It also agrees with results concerning pure shear-thinning fluids in the absence of yield stress : the shear-thinning behaviour of the fluid reduces the deposited thickness as previously observed. Last, in the limit of vanishing velocity, our scaling law predicts that the thickness of deposited YSF converges towards a finite value, which presumably depends on the microstructure of the YSF, in agreement with previous research on the topic performed in different geometries. For 0.1 < Ca < 1,the scaling law fails to describe the data. In this limit, non-linear effects must be taken into account.

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“…Generally, attention in the literature has been given to either product displacement [12][13][14] to maximize product recovery, or the removal (cleaning) of residual product. [15][16][17][18][19][20] The modeling problem, predicting the flow behavior of a high-viscosity plug, and the removal of a bound product layer, is very complex.…”

Section: Cleaning Problems In Industrymentioning

confidence: 99%

Removal of yield‐stress fluids from pipework using water

et al. 2018

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The emptying of product from process plant is a significant multiphase flow problem in food and personal care industries, controlling both product recovery, and cleaning time. Product and operational losses can be significant, especially with viscous products. It is necessary to maximize product recovery while minimizing cleaning time and effluent volume. The removal of a range of products from fully filled pipework using water has been characterized and monitored by weighing pipes at intervals and by inline turbidity probe. Data is presented for a range of products (toothpaste, hand cream, apple sauce, yoghurt, and shower gel) that have been cleaned from two pipe systems. The data can be fitted by a linear relationship between a dimensionless cleaning time, and the ratio of the product yield stress to the surface shear stress. The effect of pipe fittings is to reduce cleaning times, reflecting increased shear/energy dissipation in the pipe. V

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Two‐phase flow in a gas‐injected capillary tube

Cited by 6 publications

References 13 publications

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

Yield-stress fluid deposition in circular channels

Removal of yield‐stress fluids from pipework using water

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