A novel unified wall slip model for <scp>P</scp>oiseuille flow of polymer melt in the circular tube

Ren, Zhong; Huang, Xingyuan; Liu, Hesheng

doi:10.1002/pen.24258

Cited by 11 publications

(7 citation statements)

References 62 publications

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“…At the entrance of the channel, the volumetric flow rate of the melt is imposed with the fully developed axial velocity, v x = f ( y , Q ), v y = 0 mm/s. On the die walls, it is noted that the wall slip phenomenon has a relatively larger influence on the velocity distribution of melt inside the die, [ 33,34 ] but little impact on the viscoelastic swelling behavior of extrudate outside the die in comparison with other factors at the low apparent shear rate range. [ 5 ] Thus, to simplify the simulation, it is commonly assumed that the boundary condition is nonslip as follows: v x = v y = v z = 0 mm/s.…”

Section: Numerical Modeling and Experimental Methodsmentioning

confidence: 99%

Effect of characteristic scale on the extrudate swelling behavior of polypropylene melt in a micro‐extrusion process

Liu

Wang

et al. 2021

Polymer Engineering & Sci

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The swelling behavior in micro‐extrusion has a significant effect on the dimensional and shape accuracy of microproducts. In this study, the effect of characteristic scale, defined as the gap of die land in an annular micro‐extrusion die, on the extrudate swelling behavior of viscoelastic melt is analyzed through numerical simulations and micro‐extrusion experiments. The results show that the swelling behavior displays an obvious dependence on the characteristic scale. An increase in the characteristic scale reduces the swell ratio and retards the process to reach the equilibrium state. In contrast, a decrease in the characteristic scale results in a larger magnitude of change in velocity field and faster relaxation development of stress field. The location of the maximum velocity layer for the laminar flow gradually deviates from the geometric center of channel toward the wall of mandrel with the increase in the characteristic scale. Moreover, an increase in the flow rate results in a larger swell ratio for a constant characteristic scale. The elastic effect plays a more dominant role than the viscous effect in determining the viscoelastic swell behavior. It is imperative to consider the complicated swelling behavior and remarkable viscoelastic effect simultaneously in micro‐extrusion process.

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Section: Numerical Modeling and Experimental Methodsmentioning

confidence: 99%

Effect of characteristic scale on the extrudate swelling behavior of polypropylene melt in a micro‐extrusion process

Liu

Wang

et al. 2021

Polymer Engineering & Sci

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“…Wall slip is one of the rheological behaviors of polymer melts in the flow process and has been suggested to be true through experimentation . Molten polymers slip macroscopically over wall surfaces when the wall shear stress exceeds a critical value, this slip is known as weak slip or adhesion‐detachment wall slip, subsequently, for the linear polymer, another slip occurs when a second critical value is exceeded, which is known as the strong slip or entanglement‐disentanglement wall slip .…”

Section: Introductionmentioning

confidence: 99%

Wall Slip of Linear Polymer Melts During Ultrasonic‐assisted Micro‐injection Molding

Gao

Qiu

Ouyang

et al. 2018

Polymer Engineering & Sci

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The wall slip of linear polymer melts under ultrasonic vibration is investigated by correcting the slip mechanism, and melt flow behaviors in ultrasonic‐assisted micro‐injection molding (UμIM) method are discussed. Based on the effect mechanism of ultrasonic vibration on the melt, theoretical models of the critical shear stresses for the onset of weak and strong wall slip during UμIM are established, and the change in rheological properties due to the onset of wall slip under ultrasonic vibration is experimental investigated by a built measurement system. The results show that the onset of weak and strong wall slip of the melt in micro cavity are promoted by ultrasonic vibration, which agree with the built theoretical models, and the melt filling capability in micro cavity is enhanced by reducing apparent viscosity and releasing shear stress of the polymer melt, which improves the molding quality of micro polymer parts via UμIM method. POLYM. ENG. SCI., 59:E7–E13, 2019. © 2018 Society of Plastics Engineers

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“…However, in some cases, such as spreading of fluid on a solid surface (moving contact line) [8][9][10][11][12][13][14], corner flow [15][16][17] and extrusion of polymer melts [18][19][20], assuming no-slip at the boundary leads to velocity and stress singularities, and the breakdown of the no-slip boundary condition. While steady flow boundary conditions for simple regular interfaces are fairly well understood [21][22][23], there is still a significant void in our understanding of the behavior near the intersection of multiple interfaces, such as a moving contact line (MCL) or a corner point.…”

Section: Introductionmentioning

confidence: 99%

Unified slip boundary condition for fluid flows

Thalakkottor

Mohseni

2016

Phys. Rev. E

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Determining the correct matching boundary condition is fundamental to our understanding of several everyday problems. Despite over a century of scientific work, existing velocity boundary conditions are unable to consistently explain and capture the complete physics associated with certain common but complex problems such as moving contact lines and corner flows. The widely used Maxwell and Navier slip boundary conditions make an implicit assumption that velocity varies only in the wall normal direction. This makes their boundary condition inapplicable in the vicinity of contact lines and corner points where, velocity gradient exists both in the wall normal and wall tangential directions. In this paper, by identifying this implicit assumption we are able to extend Maxwell's slip model. Here, we present a generalized velocity boundary condition that shows that slip velocity is a function of not only the shear rate but also the linear strain rate. In addition, we present a universal relation for slip length which shows that, for a general flow, slip length is a function of the principal strain rate. The universal relation for slip length along with the generalized velocity boundary condition provides a unified slip boundary condition to model a wide range of steady Newtonian fluid flows. We validate the unified slip boundary for simple Newtonian liquids, by using molecular dynamics simulations and studying both, the moving contact line and corner flow problems.

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A novel unified wall slip model for Poiseuille flow of polymer melt in the circular tube

Cited by 11 publications

References 62 publications

Effect of characteristic scale on the extrudate swelling behavior of polypropylene melt in a micro‐extrusion process

Effect of characteristic scale on the extrudate swelling behavior of polypropylene melt in a micro‐extrusion process

Wall Slip of Linear Polymer Melts During Ultrasonic‐assisted Micro‐injection Molding

Unified slip boundary condition for fluid flows

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