Modeling the rheology of polyisobutylene solutions

Peters

et al. 1995

Journal of Rheology

SynopsisViscoelastic constitutive equations are evaluated using the benchmark problem of the planar flow past a confined cylinder for a well-characterized solution of S%(w/w) polyisobutylene in tetradecane. The ratio of channel height to cylinder diameter is equal to two. We compare finite element simulations with point-wise measured velocities and stresses obtained by means of laser Doppler anemometry and a flow-induced birefringence technique, respectively. The Deborah number (De) ranges from 0.25 to 2.32. In the case of the geometry with a symmetrically confined cylinder, computations were made with a generalized Newtonian model and with both a single-and a four-mode Phan-Thien and Tanner (PlT) model. All model parameters were determined in simple shear flow. A similar analysis is presented in case of an asymmetrically confined cylinder (with De = 1.87). Impressively good agreement was found between the predictions of the four-mode P'IT model and the measured velocities and stresses. The agreement was even excellent in the geometry with the asymmetrically confined cylinder. 0 I995 Society of Rheology.

Section: Methodsmentioning

confidence: 99%

Viscoelastic flow past a confined cylinder of a polyisobutylene solution

Peters

et al. 1995

Journal of Rheology

“…At the experimental temperatures, the polymer relaxation time τ p of the BF2 fluid, as calculated from the Oldroyd-B model (τ p = Ψ 1 /η p , where Ψ 1 and η p denote respectively the first normal stress coefficient and the polymer contribution to the viscosity), is approximately 8.5 s (Verhulst et al 2009a). Although the Oldroyd-B 7 model is frequently used to describe the rheology of Boger fluids, these fluids in principle have a spectrum of relaxation times (Quinzani et al 1990). Verhulst et al (2009a) reported that the steady rheology of BF2 can be well-described by a 5-mode Giesekus model with a longest relaxation time of 49 s. The interfacial tension of the blends was determined by fitting the slow flow droplet deformation data to the second order theory of Greco (Greco 2002).…”

Section: This Viscoelastic Materials Was Combined With Mixtures Of Polmentioning

confidence: 99%

Droplet relaxation in blends with one viscoelastic component: bulk and confined conditions

Cardinaels

Moldenaers

2010

Rheol Acta

Using a counter rotating parallel plate shear flow cell, the shape relaxation of deformed droplets in a quiescent matrix is studied microscopically. Both the effects of geometrical confinement and component viscoelasticity are systematically explored at viscosity ratios of 0.45 and 1.5. The flow conditions are varied from a rather low to a nearly critical Ca-number. Under all conditions investigated, viscoelasticity of the droplet phase has no influence on shape relaxation, whereas matrix viscoelasticity and geometrical confinement result in a slower droplet retraction. Up to high confinement ratios, the relaxation curves for ellipsoidal droplets can be superposed onto a master curve. Confined droplets with a sigmoidal shape relax in two stages; the first consists of a shape change to an ellipsoid with a limited amount of retraction, the second is the retraction of this ellipsoid. The latter can be

“…In a sequence of papers Quinzani et al [132], [133] and [134] have subsequently investigated the rheological properties of a 5 wt % polyisobutylene in tetradecane (PIB/C14) solution in relation to a number of existing constitutive models and have measured velocity and stress distributions for the flow through a planar contraction. In [133] velocity and normal stresses at a number of cross sections are measured and compared with predictions of Newtonian and power-law fluids.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

“…To study the flow around a confined cylinder, Baaijens et al [137] and [138], apply the same PIB/C14 solution as Quinzani et al [132]. Velocities and stresses are identified by means of LDV and FIB, respectively.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

Mixed finite element methods for viscoelastic flow analysis: a review

Journal of Non-Newtonian Fluid Mechanics

1998

273

150

The progress made during the past decade in the application of mixed finite element methods to solve viscoelastic flow problems using differential constitutive equations is reviewed. The algorithmic developments are discussed in detail. Starting with the classical mixed formulation, the elastic viscous stress splitting (EVSS) method as well as the related discrete EVSS and the so-called EVSS-G method are discussed among others. Furthermore, stabilization techniques such as the streamline upwind PetrovGalerkin (SUPG) and the discontinuous Galerkin (DG) are reviewed. The performance of the numerical schemes for both smooth and non-smooth benchmark problems is discussed. Finally, the capabilities of viscoelastic flow solvers to predict experimental observations are reviewed.