Mixed finite element methods for viscoelastic flow analysis: a review

Baaijens, F.P.T.

doi:10.1016/s0377-0257(98)00122-0

Cited by 272 publications

(163 citation statements)

References 162 publications

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“…[11][12][13][14][15] In CFD methods, a model constitutive equation [16][17][18][19] is used to determine the local stresses at each instant from the history of previous velocity fields. For dense polymeric liquids (melts), however, the detailed form of the constitutive relations is so complicated that they are generally unknown.…”

Section: Introductionmentioning

confidence: 99%

Multiscale Modeling for Polymeric Flow: Particle-Fluid Bridging Scale Methods

et al. 2013

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Multiscale simulation methods have been developed based on the local stress sampling strategy and applied to three flow problems with different difficulty levels: (a) general flow problems of simple fluids, (b) parallel (one-dimensional) flow problems of polymeric liquids, and (c) general (two-or three-dimensional) flow problems of polymeric liquids. In our multiscale methods, the local stress of each fluid element is calculated directly by performing microscopic or mesoscopic simulations according to the local flow quantities instead of using any constitutive relations. For simple fluids (a), such as the Lenard-Jones liquid, a multiscale method combining molecular dynamics (MD) and computational fluid dynamics (CFD) simulations is developed rather straightforwardly based on the local stationarity assumption without memories of the flow history. For polymeric liquids in parallel flows (b), the multiscale method is extended to take into account the memory effects that arise in hydrodynamic stress due to the slow relaxation of polymer-chain conformations. The memory of polymer dynamics on each fluid element is thus resolved by performing MD simulations in which cells are fixed at the mesh nodes of the CFD simulations. The complicated viscoelastic flow behaviors of a polymeric liquid confined between oscillating plates are simulated using the multiscale method. For general (two-or three-dimensional) flow problems of polymeric liquids (c), it is necessary to trace the history of microscopic information such as polymer-chain conformation, which carries the memories of past flow history, along the streamline of each fluid element. A Lagrangian-based CFD is thus implemented to correctly advect the polymerchain conformation consistently with the flow. On each fluid element, coarse-grained polymer simulations are carried out to consider the dynamics of entangled polymer chains that show extremely slow relaxation compared to microscopic time scales. This method is successfully applied to simulate a flow around a cylindrical obstacle.

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Section: Introductionmentioning

confidence: 99%

Multiscale Modeling for Polymeric Flow: Particle-Fluid Bridging Scale Methods

et al. 2013

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“…For both viscoelastic constitutive models, we employ the DEVSS-Gscheme [28][29][30] for stability. The SUPGmethod [31] and the log-conformation approach [32,33] are used to describe the evolution equation for the conformation tensor.…”

Section: Moving Domainmentioning

confidence: 99%

Sintering of Two Viscoelastic Particles: A Computational Approach

2017

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Selective laser sintering (SLS) is a high-resolution additive manufacturing fabrication technique. To fully understand the process, we developed a computational model, using the finite element method, to solve the flow problem of sintering two viscoelastic particles. The flow is assumed to be isothermal and the particles to be in a liquid state, where their rheology is described using the Giesekus and XPP constitutive models. In this work, we assess the parameters that define this problem, such as the initial geometry, the Deborah number and other dimensionless parameters present in the rheological models. In particular, the conformation tensor is considered, which is a measure for the polymeric strain and plays an important role in the crystallization kinetics of semicrystalline polymers like polyamide 12, usually used in SLS.

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“…Paralelamente, a pesquisa sobre a simulação numérica de escoamentos de fluidos viscoelásticos tem sido bastante intensa desde a década de 70 [6] , sendo que muitas metodologias têm sido propostas, com base em diferentes métodos numéricos [7][8][9] . Além disso, já existem também versões de solvers para escoamentos de fluidos viscoelásticos de código aberto disponibilizados em softwares livres [10,11] .…”

Section: Farias T M Et Al -Utilização Da Técnica De Birrefringêncunclassified

Utilização da técnica de birrefringência em reômetro multipasse para a diferenciação de grades de poliestireno cristal

et al. 2014

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Resumo: O entendimento de como as propriedades reológicas afetam o comportamento dos polímeros nas operações de processamento, por meio de diferentes técnicas experimentais, é de fundamental importância para ser possível prever e avaliar a estrutura final destes materiais. Neste contexto, o objetivo deste trabalho é aplicar a técnica de birrefringência para diferenciar dois grades de poliestireno cristal. Foram realizados experimentos em um reômetro multipasse que permitiram a aquisição de imagens de birrefringência, que representam o campo de tensão do escoamento, e obteve-se a queda de pressão durante os experimentos. Ao se compararem os padrões de birrefringência dos dois poliestirenos foi possível distinguir os materiais e verificar que o escoamento da amostra de maior massa molar é mais complexo, com maior birrefringência e tensão mais elevada. Os resultados obtidos, além de contribuírem para a caracterização reológica, podem ser empregados no estudo comparativo de modelos constitutivos e desenvolvimento de códigos computacionais. Palavras-chave:Birrefringência, reômetro multipasse, poliestireno. The Use of Birefringence Technique in a Multipass Rheometer for the Differentiation of General Purpose Polystyrene GradesAbstract: Polymers must go through processes that transform raw materials in a final product for consumption, and therefore it is crucial to understand how their rheological properties affect processability and final product quality. This study is aimed at applying the birefringence technique to differentiate two grades of general purpose polystyrene. Flow experiments were carried out using a multi-pass rheometer and flow-induced birefringence images and pressure profile were obtained. It was possible to distinguish between the different materials by examining their birefringence patterns. The flow of the higher molecular weight sample is more complex, with higher birefringence and tension. These data are important for the rheological characterization of the material and can be used in the validation of constitutive models in computational fluid dynamics. Universitária, Fundão, Av. Horácio Macedo, 2030, CEP 21941-914, Rio de Janeiro, RJ, Brasil, e-mail: arge@peq.coppe.ufrj.br Introdução O conhecimento do comportamento reológico de polímeros fundidos é de suma importância nas operações que transformam a matéria-prima em produto final para o consumo. Polímeros, tais como polietileno, polipropileno, policarbonato e poliestireno, são processados em elevadas temperaturas e, durante as operações como extrusão e moldagem por injeção, o material é submetido a altas taxas de deformação, causando a orientação e alongamento das cadeias. O processamento de polímeros é diretamente afetado pelas propriedades reológicas em estado fundido, sendo necessário conhecer o comportamento desses materiais nas condições práticas de escoamento para ser possível prever e avaliar a estrutura final do material [1] . Assim, com o intuito de evitar ou diminuir a necessidade de procedimentos de tentativa e erro, que represe...

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Mixed finite element methods for viscoelastic flow analysis: a review

Cited by 272 publications

References 162 publications

Multiscale Modeling for Polymeric Flow: Particle-Fluid Bridging Scale Methods

Multiscale Modeling for Polymeric Flow: Particle-Fluid Bridging Scale Methods

Sintering of Two Viscoelastic Particles: A Computational Approach

Utilização da técnica de birrefringência em reômetro multipasse para a diferenciação de grades de poliestireno cristal

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