Some elasto-viscoplastic preliminary results obtained at the Laboratory of Applied and Computational Fluid Mechanics (LAMAC) from the Federal University of R

For elastoviscoplastic materials undergoing LAOS in these geometries, both elastic but flexible model that is popular for use with fluids that exhibit a yield stress. Because the transitions from elastic to viscoplastic behavior d

de Souza Mendes, P. R., and R. L. Thompson, “ A unified approach to model elasto-viscoplastic thixotropic yield-stress materials and apparent yield-stress fluids,” Rheol. Acta 52 , 673– 694 (2013). Originally it was believed that YS materials are just generalized Newtonian fluids, i.e. fluids with a viscosity that depends on the strain-rate when the yield-stress is exceeded. Recent experiments have shown that most of them exhibit also elastic, hence the term elasto-viscoplastic (EVP), and thixotropic (hence, TEVP) properties. We investigate the radial oscillations of small gas bubbles trapped in yield-stress fluids and driven by an acoustic pressure field.

Yet, the velocity fields in the viscoplastic and elastoviscoplastic flows are comparable for small elastic effects. By increasing the yield stress, the difference in the pressure drops between the two classes of flows becomes smaller and smaller for both considered geometries. An analytical study of elastoviscoplastic fluid flow in tubes of non-circular cross section is presented. The constitutive structure of the fluid is described by a linear frame invariant combination of the Phan-Thien−Tanner model of viscoelastic fluids and the Bingham model of plastic fluids. they behave as purely viscous fluids, with constant or shear thinning viscosity. Viscoplastic fluids can present elasticity and thixotropy.

Yet, the velocity fields in the viscoplastic and elastoviscoplastic flows are comparable for small elastic effects. By increasing the yield stress, the difference in the pressure drops between the two classes of flows becomes smaller and smaller for both considered geometries.

Fluid Mech. 158, 154 (2009)].

Viscoplastic and elastoviscoplastic fluids

Here, we focus on elastoviscoplastic fluids, i.e. complex non-Newtonian fluids that can exhibit simultaneously elastic, viscous and plastic properties. In particular, they behave as solids when the applied stress is below a certain threshold $\unicode[STIX]{x1D70F}_{0}$ , i.e. the yield stress, while for stresses above it, they start to flow as liquids.

Here, we focus on fluids that can exhibit simultaneously elastic, viscous and plastic properties, usually called elastoviscoplastic (EVP) fluids (Balmforth, Frigaard & Ovarlez 2014). International audienceFrom a thermodynamic theory, a new model for elastoviscoplastic fluid flow is presented. It extends the Bingham viscoplastic model and the Oldroyd viscoelastic model. Fundamental flows are studied: simple shear flow, uniaxial elongation and large amplitude oscillatory shear. We model the rheological behavior of the yield-stress fluid using the recently developed elastoviscoplastic constitutive equation that takes into account the elastic and viscoplastic deformations Viscoplastic fluids exhibit a threshold in applied stress (yield stress) below which the material behaves like an elastic solid, and above which it flows like a liquid. Bubbles are therefore harder to remove from a viscoplastic fluid than from a simple viscous fluid: in the regime where the material behaves like a solid, the bubbles are The collision of drops in a solid substrate is an interesting problem with several practical applications.

Recently, an Oldroyd-B type constitutive equation was proposed by (de Souza Mendes, 2009) to model the behavior of elasto-viscoplastic fluids, and also thixotropy. The equation involves the Emad Chaparian, Daulet Izbassarov, Francesco De Vita, Luca Brandt, Outi Tammisola, Yield-stress fluids in porous media: a comparison of viscoplastic and elastoviscoplastic flows, Meccanica, 10.1007/s11012-019-01010-6, (2019).
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They demonstrate the viscous effects always as before as after exceedition of yield limit. • Among many viscoplastic fluids, there is a special class called Bingham plastics. For Bingham plastic fluid, the shear stress beyond the yield stress is linearly the classical J2-viscoplasticity with a flow criterion expressed in the current In this elasto-viscoplastic formulation, the effective stress ¯σ is no longer In elasto-viscoplastic analysis, the use of implicit time integration techniques is advantageous or even unavoidable.

Recently, an Oldroyd-B type constitutive equation was proposed by (de Souza Mendes, 2009) to model the behavior of elasto-viscoplastic fluids, and also thixotropy. The equation involves the In this paper, a three‐dimensional numerical solver is developed for suspensions of rigid and soft particles and droplets in viscoelastic and elastoviscoplastic (EVP) fluids.
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In this paper, a three‐dimensional numerical solver is developed for suspensions of rigid and soft particles and droplets in viscoelastic and elastoviscoplastic (EVP) fluids.

viscoplastic and elastoviscoplastic ﬂows are compa-rable for small elastic effects. By increasing the yield stress,thedifferenceinthepressuredropsbetweenthe two classes of ﬂows becomes smaller and smaller for both considered geometries. When the elastic effects increase, the elastoviscoplastic ﬂow becomes time- In this work, we solve the full Cauchy equations governing the inertial flows of a viscoplastic fluid (Bingham model) and elastoviscoplastic fluid (Saramito model). The focus is on the motion of a yield-stress fluid through a solid matrix (model porous media).