Characterising wall-slip behaviour of carbopol gels in a fully-developed poiseuille flow

Daneshi, Masoud; Pourzahedi, Ali; Martinez, D. Mark; Grecov, Dana

doi:10.1016/j.jnnfm.2019.06.003

Cited by 23 publications

(27 citation statements)

References 22 publications

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“…To verify the velocity profile across the cell, we undertook some separate studies of flow down a uniform slot with treated walls, combining optical coherence tomography (Thorlabs TEL1300V2-BU) with particle-tracking velocimetry [20,21]. Sample profiles are presented in Fig.…”

Section: Concentrationmentioning

confidence: 99%

Obstructed viscoplastic flow in a Hele-Shaw cell

et al. 2020

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Experiments are conducted exploring the flow of Carbopol past obstacles in a narrow slot and compared with predictions of a model based on the Herschel-Bulkley constitutive law and the conventional Hele-Shaw approximation. Although Carbopol is often assumed to be a relatively simple yield-stress fluid, the flow pattern around an obstacle markedly lacks the fore-aft symmetry expected theoretically. Such asymmetry has been observed previously for viscoplastic flows past obstacles in unconfined geometries, but the narrowness of the Hele-Shaw cell ensures that the stress state is very different, placing further constraints on the underlying origin. The asymmetry is robust, as demonstrated by varying the shape and number of the obstacles, the surfaces of the cell walls, and the steadiness of the flow rate. The results suggest that rheological hysteresis near the yield point may be the cause of the asymmetry.

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Section: Concentrationmentioning

confidence: 99%

Obstructed viscoplastic flow in a Hele-Shaw cell

et al. 2020

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“…The case τc*=τ0*, which is the simplest of all, since material yielding and wall slip occur simultaneously, is examined first. Then, the case τc*<τ0*, which is more relevant to experimental observations [20,22], is analyzed.…”

Section: Solution With Non-zero Slip Yield Stressmentioning

confidence: 99%

“…For example, for microgel pastes Seth et al [29] reported values of τc* and τ0* in the ranges 3.2–6 Pa and 53–117 Pa, respectively. Similarly, Piau [21] reported values in the ranges 0.23–23 Pa and 22–94 Pa. Daneshi et al [22] reported that for water-based Carbopol gels with a concentration greater than 0.075%, the slip yield stress increases linearly with the yield stress, τc*=false(0.18±0.02false) τ0*, and roughly linearly with the solvent viscosity.…”

Section: Introductionmentioning

confidence: 98%

“…Equation (2) has also been used to describe strong slip of polymer melts, in which case s is in the range 2.5–3.3 [11]. In the case of Carbopol gels, various values for the exponent have been reported at different concentrations, in the range 0.87≤s≤2 (see [22] and references therein). Setting s=1 in Equation (2) yields uw*={left0,τw*≤τc*τw*−τc*β*,τw*>τc*, which has been proposed for Newtonian fluids by Spikes and Granick [12], who tested the applicability of the above equation on experimental data and discussed possible physical mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Viscoplastic Couette Flow in the Presence of Wall Slip with Non-Zero Slip Yield Stress

2019

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The steady-state Couette flow of a yield-stress material obeying the Bingham-plastic constitutive equation is analyzed assuming that slip occurs when the wall shear stress exceeds a threshold value, the slip (or sliding) yield stress. The case of Navier slip (zero slip yield stress) is studied first in order to facilitate the analysis and the discussion of the results. The different flow regimes that arise depending on the relative values of the yield stress and the slip yield stress are identified and the various critical angular velocities defining those regimes are determined. Analytical solutions for all the regimes are presented and the implications for this important rheometric flow are discussed.

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“…In the Carbopol group, Carbopol 940 is considered to possess the greatest viscosity and has the advantage of forming a high‐viscosity gel at a very low concentration and can maintain a gel‐like state after it is combined with Zn to form Zn gel, which has a long‐term stability . Zn powder blended with Carbopol 940 in KOH electrolyte was combined to form Zn gel, which can be squeezed into the cell for gel replenishment, and the aqueous soluble intermediate of zincate can be removed simultaneously via liquid circulation before forming solid passivation layers.…”

Section: Introductionmentioning

confidence: 99%

Discharge performance of Zn‐air fuel cells under the influence of Carbopol 940 thickener

et al. 2020

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Summary A dynamic research endeavor has been performed in this research study by constructing and operating an innovative flowing type anode (zinc gel) along with Carbopol 960 additives as thickener in a zinc‐air fuel cell. This gel constituted of a mixture of Zn powder, thickener, and potassium hydroxide (KOH) electrolyte, and it was fueled into the cell with a peristaltic pump. The flowing Zn anode allowed the reaction‐produced water, carbonate, and zinc oxide (ZnO) to be discharged from the cell. Basic operating parameters of the fuel cell like the concentrations of the Zn powder, thickener, and electrolyte along with the number and grid density of the current collector grid, cell operation temperature, and air flow rate were all optimized for effective and enhanced fuel cell performance. It was determined based on voltage production along with current and energy density generation. The augmented experimental results were as follows; thickener concentration of 1 to 2 wt% was observed to be optimum above which the electrolyte acquired a solid state. The voltage production was stable at electrolyte concentrations of 60 to 65 wt% and Zn powder concentrations lower than 40 wt%, and concentrations greater than this resulted in reduced cell performance. The implementation of four current collector grids each with an opening density of 144 grid/cm2 had efficiently amplified cell performance. The ideal cell temperature was determined to be 40°C, and maximum cell production was attained at an air flow rate of 2 m/s. Consequently, effective improvement and advancement in the processes and operational parameters were achieved in this zinc‐air fuel cell with a state‐of‐the‐art anode fuel. This will surely provide great opportunities for their applications in the future.

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Characterising wall-slip behaviour of carbopol gels in a fully-developed poiseuille flow

Cited by 23 publications

References 22 publications

Obstructed viscoplastic flow in a Hele-Shaw cell

Obstructed viscoplastic flow in a Hele-Shaw cell

Viscoplastic Couette Flow in the Presence of Wall Slip with Non-Zero Slip Yield Stress

Discharge performance of Zn‐air fuel cells under the influence of Carbopol 940 thickener

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