Journal article 631 views
Viscoelastic computations for reverse roll coating with dynamic wetting lines and the Phan-Thien-Tanner models
Shirley O. S. Echendu,
Hamid R. Tamaddon-Jahromi,
Mike F. Webster,
Michael Webster 
Rheologica Acta, Volume: 53, Issue: 4, Pages: 315 - 331
Swansea University Author:
Michael Webster
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DOI (Published version): 10.1007/s00397-014-0761-7
Abstract
The computational modelling of reverse roll coating with dynamic wetting line were analysed for various non-Newtonian viscoelastic materials appealing to Phan-Thien Tanner (PTT) network class of models suitable for typical polymer solutions, with properties of shear-thinning and strain-hardening/sof...
| Published in: | Rheologica Acta |
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| Published: |
2014
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa24190 |
| Abstract: |
The computational modelling of reverse roll coating with dynamic wetting line were analysed for various non-Newtonian viscoelastic materials appealing to Phan-Thien Tanner (PTT) network class of models suitable for typical polymer solutions, with properties of shear-thinning and strain-hardening/softening. The numerical technique utilises a hybrid finite element-subcell finite volume algorithm with dynamic free-surface location, drawing upon a fractional staged predictor-corrector semi-implicit time-stepping procedure of incremental pressure-correction form. The numerical solution is investigated following a systematic study which allows for parametric variation in elasticity (We-variation), extensional hardening-softening (ε), and solvent fraction (β). Under incompressible liquid flow conditions, LPTT and EPTT models were used to solve the paint strip coatings, in reverse roll coating configuration. This involves two dimensional planar reverse roll coating domains, considering a range of Weissenberg numbers (We) up to critical levels, addressing velocity fields and vortex developments, pressure and lift profiles, shear-rate and stress fields. Various differences are observed comparing solutions for these constitutive models. Concerning the effects of elasticity, increase in We stimulates vortex structures which are visible at both downstream meniscus and upstream narrowest nip region, whilst decreasing the peak pressure and lift values at the nip constriction. At low values (ε>0.5, β=0.1 ) of extensional viscosity, LPTT model flow fields were much easier to extract attaining critical We levels up to unity, in contrast to critical We levels of 0.4 for EPTT solutions; the position is reversed at higher extensional viscosity levels (ε<0.5). This trend reveals qualitative agreement with theoretical studies. Noting influence under EPTT solution, increasing the peak level of extensional hardening/softening stimulates vortex activity around the nip region, with corresponding increase in peak pressure and lift values. |
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| Keywords: |
Reverse roller coating, free surface, dynamic wetting, finite elements, finite volume sub-cell, viscoelastic Phan-Thien Tanner models. |
| College: |
Faculty of Science and Engineering |
| Issue: |
4 |
| Start Page: |
315 |
| End Page: |
331 |