Strain mode of general flow: Characterization and implications for flow pattern structures

Nakayama, Yasuya; Kajiwara, Toshihisa; Masaki, Tatsunori

doi:10.1002/aic.15228

Cited by 25 publications

(19 citation statements)

References 35 publications

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“…Figure c shows β distribution in the axial cross‐section indicated in Figure b. The distribution of the strain‐rate state reflects the local flow pattern and therefore is useful for discussing the relation between the geometry and the flow pattern …”

Section: Resultsmentioning

confidence: 99%

“…We consider two different tip angles, namely forward and backward tip angles, on FKD as well as the conventional one, and discuss the differences in the flow patterns and the mixing abilities of the different geometries using numerical simulations of the flow in the kneading block zone. In order to discuss the flow pattern structures by different kneading blocks, we observe the strain‐rate state distribution as well as the velocity field. For quantification of the distributive mixing, we used the statistical distribution of the finite‐time Lyapunov exponent (FTLE) in addition to the residence time distribution.…”

Section: Introductionmentioning

confidence: 99%

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Improving mixing characteristics with a pitched tip in kneading elements in twin‐screw extrusion

et al. 2017

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In twin‐screw extrusion, the geometry of a mixing element mainly determines the basic flow pattern, which eventually affects the mixing ability as well as the dispersive ability of the mixing element. The effects of geometrical modification, with both forward and backward pitched tips, of a conventional forward kneading disks element (FKD) in the pitched‐tip kneading disks element on the flow pattern and mixing characteristics are discussed. Numerical simulations of fully filled, nonisothermal polymer melt flow in the melt‐mixing zone were performed, and the flow pattern structure and the tracer trajectories were investigated. The pitched tips largely affect the inter‐disk fluid transport, which is mainly responsible for mixing. These changes in the local flow pattern are analyzed by the distribution of the strain‐rate state. The distribution of the finite‐time Lyapunov exponent reveals a large inhomogeneity of the mixing in FKD is suppressed both by the forward and backward tips. By the forward tips on FKD, the mixing ability is relatively suppressed compared to FKD, whereas for the backward tips on FKD, the mixing ability is enhanced while maintaining the same level of dispersion efficiency as FKD. From these results, the pitched tips on the conventional KD turn out to be effective at reducing the inhomogeneity of the mixing and tuning the overall mixing performance. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1424–1434, 2018

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improving mixing characteristics with a pitched tip in kneading elements in twin‐screw extrusion

et al. 2017

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“…As reported, melt drops of high viscosity ratio blends are more efficiently broken under an extensional flow than under a shear flow . The flow field of TSE is usually dominated by shear flow, but special screw elements or configurations could enhance the elongational effect . In general, the generation of an extensional flow is based on converging channels; however, most of these flow fields are local or fixed .…”

Section: Introductionmentioning

confidence: 92%

Effects of extensional flow on properties of polyamide‐66/poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends: A study of morphology, mechanical properties, and rheology

Yang

Xin

Huang

et al. 2016

Polymer Engineering & Sci

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In this study, polyamide-66/poly(2,6-dimethyl-1,4-phenylene oxide) (PA66/PPO) blends with high viscosity ratio were processed by a self-designed triangle-arrayed triple-screw extruder (TTSE, which simulates extensional flow) and a commercial twin-screw extruder (TSE), respectively. Furthermore, in order to improve the mechanical properties of the immiscible PA66/PPO blends, PPO-grafted maleic anhydride (PPO-g-MA) and styrene-ethylene-butylene-styrene (SEBS) block copolymer were used. The mechanical properties, phase morphology, and rheological properties of both binary PA66/PPO blends and toughened PA66/PPO/ PPO-g-MA blends were comprehensively investigated to compare the above mentioned two processing method. Samples processed with TTSE exhibited better mechanical properties than the TSE-processed blends. The morphologies of the blends were examined by scanning electron microscopy, exhibiting smaller particles sizes and narrower particle size distributions, which were attributed to the significant effects of extensional flow in TTSE. The toughening mechanism of compatibilized blends was investigated through morphology analysis, dynamic mechanical, and rhelogical analysis. Thus, TTSE with an extensional effect was proved to be efficient in the blending of high viscosity ratio polymers.

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“…It is worth noting that during the preparation of the present article we have become aware of a very recent paper by Nakayama et al [21], in which the parameter R N is proposed for characterization of flow patterns in complex mixers.…”

Section: Droplet Break-up In 3d Laminar Flowsmentioning

confidence: 99%

Computational Fluid Dynamics (CFD)-Based Droplet Size Estimates in Emulsification Equipment

Janssen

Mayer²

2016

Processes

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While academic literature shows steady progress in combining multi-phase computational fluid dynamics (CFD) and population balance modelling (PBM) of emulsification processes, the computational burden of this approach is still too large for routine use in industry. The challenge, thus, is to link a sufficiently detailed flow analysis to the droplet behavior in a way that is both physically relevant and computationally manageable. In this research article we propose the use of single-phase CFD to map out the local maximum stable droplet diameter within a given device, based on well-known academic droplet break-up studies in quasi-steady 2D linear flows. The results of the latter are represented by analytical correlations for the critical capillary number, which are valid across a wide viscosity ratio range. Additionally, we suggest a parameter to assess how good the assumption of quasi-steady 2D flow is locally. The approach is demonstrated for a common lab-scale rotor-stator device (Ultra-Turrax, IKA-Werke GmbH, Staufen, Germany). It is found to provide useful insights with minimal additional user coding and little increase in computational effort compared to the single-phase CFD simulations of the flow field, as such. Some suggestions for further development are briefly discussed.

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Strain mode of general flow: Characterization and implications for flow pattern structures

Cited by 25 publications

References 35 publications

Improving mixing characteristics with a pitched tip in kneading elements in twin‐screw extrusion

Improving mixing characteristics with a pitched tip in kneading elements in twin‐screw extrusion

Effects of extensional flow on properties of polyamide‐66/poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends: A study of morphology, mechanical properties, and rheology

Computational Fluid Dynamics (CFD)-Based Droplet Size Estimates in Emulsification Equipment

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