Mixing viscoplastic fluids in stirred vessels over multiple scales: A combined experimental and CFD approach

Russell, Andrew; Kahouadji, Lyes; Mirpuri, Karan; Quarmby, Andrew; Piccione, Patrick M.; Matar, Omar; Luckham, P.F.; Markides, Christos N.

doi:10.1016/j.ces.2019.07.047

Cited by 33 publications

(19 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The residual values should be verified and reported, which is not always done. [6,9,14,15,18,25,31,33] In this work, all the simulations reached residuals values below 10 À5 at every time step. From the graphs of the monitored variables, nonphysical oscillations and numerical instabilities were discarded.…”

Section: Simulation Completion Criteriasupporting

confidence: 49%

“…The residual values should be verified and reported, which is not always done. [ 6,9,14,15,18,25,31,33 ] In this work, all the simulations reached residuals values below 10 −5 at every time step.…”

Section: Resultsmentioning

confidence: 62%

“…Some publications assessed the grid but not the time step. [7,[16][17][18][19] Other articles used a heuristic based on the impeller speed to set the upper limit of the time-step size. [20] Although this can be a good starting point to select an initial time step, the time-step sensitivity should be studied.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Computational modelling of mixing tanks for bioprocesses: Developing a comprehensive workflow

et al. 2021

View full text Add to dashboard Cite

This paper reports a computational modelling study of a mixing tank for bioprocess applications. A dual impeller mixer containing several probes is used with a mixing speed of 400 rpm. The single-phase transient model is validated against experimental measurements using torque and velocity profiles as the validation variables. A complete workflow is illustrated that addresses all the relevant steps in the modelling of mixing. Many assumptions that are commonly made are explored and their importance is demonstrated. The necessity of including the probes in the computational domain is illustrated. The grid and time-step size are examined, and the relationship between the two is explained. Two turbulence models for RANS equation closure are compared, and the efficacy of the appropriate solution methodology for each is described.The importance of using the correct near-wall treatment is shown. Overall, this paper presents a standardized framework for the modelling of mixing tanks with turbulent flow.

show abstract

Section: Simulation Completion Criteriasupporting

confidence: 49%

Section: Resultsmentioning

confidence: 62%

See 1 more Smart Citation

Computational modelling of mixing tanks for bioprocesses: Developing a comprehensive workflow

et al. 2021

View full text Add to dashboard Cite

show abstract

“…The flow domain is a tube of circular cross-section of diameter D and length 27.8D, which is modeled with a three-dimensional geometry. The walls of the tube are constructed via a module that defines solid objects by means of a signed distance function, an approach that was previously adopted for more complex geometries when using the present numerical solver [19,32]. The elongated bubble is initially located at the beginning of the channel and its shape is initialised using a cylindrical body with a cross-sectional diameter D b = 0.94D, and two hemispherical caps at its two ends, as indicated in Fig.…”

Section: B Problem Statement and Validationmentioning

confidence: 99%

Effect of surfactant on elongated bubbles in capillary tubes at high Reynolds number

Batchvarov¹,

Kahouadji²,

Magnini³

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

The effect of surfactants on the tail and film dynamics of elongated gas bubbles propagating through circular capillary tubes is investigated by means of an extensive three-dimensional numerical study using a hybrid front-tracking/level-set method. The focus is on the visco-inertial regime, which occurs when the Reynolds number of the flow is much larger than unity. Under these conditions, 'clean' bubbles exhibit interface undulations in the proximity of the tail [25], with an amplitude that increases with the Reynolds number. We perform a systematic analysis of the impact of a wide range of surfactant properties, including elasticity, bulk surfactant concentration, solubility, and diffusivity, on the bubble and flow dynamics in the presence of inertial effects. The results show that the introduction of surfactants is effective in suppressing the tail undulations as they tend to accumulate near the bubble tail. Here, large Marangoni stresses are generated, which lead to a local 'rigidification' of the bubble. This effect becomes more pronounced for larger surfactant elasticities and adsorption depths. At reduced surfactant solubility, a thicker rigid film region forms at the bubble rear, where a Couette film flow is established, while undulations still appear at the trailing edge of the downstream 'clean' film region. In such conditions, the bubble length becomes an influential parameter, with short bubbles becoming completely rigid.

show abstract

“…Since the viscosity of non‐Newtonian fluids depends on the shear rate, some problems such as complex flow, 20,21 formation of dead zones, 22–24 low mixing efficiency, and considerable energy consumption 25,26 arise in the mixing process. Hence, many investigations have focused on the mixing characteristics of different non‐Newtonian fluids 27–32 .…”

Section: Introductionmentioning

confidence: 99%

Study of hydrodynamics and flow characteristics in a twin‐blade planetary mixer with non‐Newtonian fluids

et al. 2022

View full text Add to dashboard Cite

This study aims to characterize the hydrodynamics and flow characteristics in a twin‐blade planetary mixer with non‐Newtonian fluids by using CFD modeling technique. The kneading pressure was recorded using an experimental setup, and a CFD model was verified. The flow characteristics and hydrodynamics in the mixing vessel containing the power‐law fluids were analyzed quantitatively, particularly the influence of the flow behavior index n. Results revealed that as n increased from 0.25 to 1.75, the maximum shear rate decreased from 733 to 120 s−1 and the local apparent viscosity in the kneading regions increased significantly. The maximum kneading pressure and power consumption increased almost exponentially with increasing n. The correlation for the kneading pressure and the correlation for the power consumption were established by introducing the pressure‐oriented effective viscosity μe‐p, the pressure‐oriented effective shear rate trueγ̇e−p, the improved effective viscosity μei and the improved effective shear rate trueγ̇italicei.

show abstract

Mixing viscoplastic fluids in stirred vessels over multiple scales: A combined experimental and CFD approach

Cited by 33 publications

References 69 publications

Computational modelling of mixing tanks for bioprocesses: Developing a comprehensive workflow

Computational modelling of mixing tanks for bioprocesses: Developing a comprehensive workflow

Effect of surfactant on elongated bubbles in capillary tubes at high Reynolds number

Study of hydrodynamics and flow characteristics in a twin‐blade planetary mixer with non‐Newtonian fluids

Contact Info

Product

Resources

About