Persona:
Español Garrigos, José

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0000-0001-5263-2817
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Español Garrigos
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José
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2019 - 201912020 - 20231
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Autor: Ellero, Marco × search.filters.applied.f.itemDepartamento: Física Fundamental ×

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Mostrando 1 - 2 de 2
  • Miniatura
    Publicación
    Shear thickening of a non-colloidal suspension with a viscoelastic matrix
    (Cambridge University Press, 2019) Vázquez Quesada, Adolfo; Español Garrigos, José; Tanner, Roger I.; Ellero, Marco; https://orcid.org/0000-0003-1365-6052; https://orcid.org/0000-0001-8894-0395
    We study the rheology of a non-colloidal suspension of rigid spherical particles interacting with a viscoelastic matrix. Three-dimensional numerical simulations under shear flow are performed using the smoothed particle hydrodynamics method and compared with experimental data available in the literature using different constant-viscosity elastic Boger fluids. The rheological properties of the Boger matrices are matched in simulation under viscometric flow conditions. Suspension rheology under dilute to semi-concentrated conditions (i.e. up to solid volume fraction ϕ=0.3 ) is explored. It is found that at small Deborah numbers De (based on the macroscopic imposed shear rate), relative suspension viscosities ηr exhibit a plateau at every concentration investigated. By increasing De , shear thickening is observed, which is related to the extensional thickening of the underlying viscoelastic matrix. Under dilute conditions ( ϕ=0.05 ), numerical results for ηr agree quantitatively with experimental data in both the De and ϕ dependences. Even under dilute conditions, simulations of full many-particle systems with no a priori specification of their spatial distribution need to be considered to recover precisely experimental values. By increasing the solid volume fraction towards ϕ=0.3 , despite the fact that the trend is well captured, the agreement remains qualitative with discrepancies arising in the absolute values of ηr obtained from simulations and experiments but also with large deviations existing among different experiments. With regard to the specific mechanism of elastic thickening, the microstructural analysis shows that elastic thickening correlates well with the average viscoelastic dissipation function θelast , requiring a scaling as ⟨θelast⟩∼Deα with α⩾2 to take place. Locally, despite the fact that regions of large polymer stretching (and viscoelastic dissipation) can occur everywhere in the domain, flow regions uniquely responsible for the elastic thickening are well correlated to areas with significant extensional component.
  • Miniatura
    Publicación
    Non-affine motion and selection of slip coefficient in constitutive modelling of polymeric solutions using a mixed derivative
    (American Institute of Physics, 2023-01) Nieto Simavilla, David; Español Garrigos, José; Ellero, Marco
    Constitutive models for the dynamics of polymer solutions traditionally rely on closure relations for the extra stress or related microstructural variables (e.g., conformation tensor) linking them to flow history. In this work, we study the eigendynamics of the conformation tensor within the GENERIC framework in mesoscopic computer simulations of polymer solutions to separate the effects of nonaffine motion from other sources of non-Newtonian behavior. We observe that nonaffine motion or slip increases with both the polymer concentration and the polymer chain length. Our analysis allows to uniquely calibrate a mixed derivative of the Gordon–Schowalter type in macroscopic models based on a micro-macromapping of the dynamics of the polymeric system. The presented approach paves the way for better polymer constitutive modeling in multiscale simulations of polymer solutions, where different sources of non-Newtonian behavior are modelled independently.