Boger fluid

Mitsoulis, E., 1986. The numerical simulation of Boger fluids a viscometric approximation approach. Polym. Eng. Sci. 26, 1552-1562. 

Fig. 13.35 Fractional coverage results for the Boger fluids (open circles) compared to experiments (solid triangles). [Reprinted by permission from V. Gauri and K. W. Koelling, Gas-assisted Displacement of Viscoelastic Fluids Flow Dynamics at the Bubble Front, J. Non-Newt. Fluid Mech., 83, 183-203 (1999).]...

In the story of numerical flow simulation, the ability to predict observed and significant viscoelastic flow phenomena of polymer melts and solutions in an abrupt contraction has been unsuccessful for many years, in relation to the incomplete rheological characterization of materials, especially in elongation. The numerical treatments have often been confined to flow of elastic fluids with constant viscosity, described by differential constitutive equations as the Upper Convected Maxwell and Oldroyd-B models. Fortunately, the recent possibility to use real elastic fluids with constant viscosity, the so-called Boger fluids [10], has narrowed the gap between experimental observation and numerical prediction [11]. 

Figure 3.2 Trouton ratio, Tr, of uniaxial extensional viscosity to zero-shear viscosity jq after start-up of steady uniaxial extension at a rate of 1 sec i for a Boger fluid consisting of a 0.185 wt% solution of flexible polyisobutylene (Mu, = 2.11 x 10 ) in a solvent composed mostly of viscous polybutene with some added kerosene (solid line). The dashed line is a fit of a multimode FENE dumbbell model, where each mode is represented by a FENE dumbbell model, with a spring law given by Eq. (3-56), without preaveraging, as described in Section 3.6.2.2.I. The relaxation times were obtained by fitting the linear viscoelastic data, G (co) and G"(cu). The slowest mode, with ri = 5 sec, dominates the behavior at large strains the best fit is obtained by choosing for it an extensibility parameter of = 40,000. The value of S — = 3(0.82) n/C(x, predicted from the...

Y. L. Joo and E. S. G. Shaqfeh, Observations of purely elastic instabilities in the Taylor-Dean flow of a Boger fluid, J. Fluid Mech. 262, 21-1A (1994). 

Both liquids were of the Boger fluid type. For a given matrix, the drop deformability decreased with elasticity of the dispersed phase. For a given drop liquid, the drop deformability increased with the matrix elasticity. The following empirical equation was proposed ... 

The deformability of the viscoelastic drops in Newtonian matrix was studied in the convergent slit flow. Both, the experimental observations and the boundary element method computations were carried out. It was reported that deformation of the Boger fluid drop, was quite low —about 1/3 of that recorded for the deformability of a strongly shear-thinning, viscoelastic solution. The latter drops showed deformability similar to these observed for Newtonian drops of similar viscosities. 

Thus, the complete definition of a Newtonian fluid is that it not only possesses a constant viscosity but it also satisfies the condition of equation (1.9), or simply that it satisfies the complete Navier-Stokes equations. Thus, for instance, the so-called constant viscosity Boger fluids [Boger, 1976 Prilutski et al., 1983] which display constant shear viscosity but do not conform to equation (1.9) must be classed as non-Newtonian fluids. 

Rodrigue et al. (1994) Cylinders, bars, and irregular-shaped rock particles Carreau fluid model Extensive results on drag in pseudoplastic, viscoelastic, and Boger fluids, Re< 50... 

The only drag measurements on nonspherical particles (cylinders, bars) in viscoelastic fluids are due to Rodrigue et al. (1984). They measured free-settling velocities in a polyisobutylene in kerosene/polybutene solution (Boger fluid), with a fluid relaxation time of 7.2 msec. They found it necessary to modify Eq. (16) by incorporating the following correction factor due to viscoelasticity ... 

Although the UCM equation gives the polymer contribution to the stress in a dilute solution such as a Boger fluid, the solvent contribution to the stress cannot be neglected, and so the total stress tensor r in these solutions is the sum of the polymeric and solvent contributions... 

Figure 7.8.S shows the flow field for a Boger fluid obtained by Binding and Walters (1988). The pictures show that as the flow rate increases, vortices generated in the comers of the contraction increases in size as a result of the extension-thickening nature of the fluid.

Flow fields of a Boger fluid at various flow rates in an axisymmetric contraction with a contraction ratio of 14.375 (A) Q = 0.08 mL/s, (B)... 

James DF. Boger fluids. Annu Rev Huid Mech 2009 41 129-142. 

Arigo McKinley, J. Rheol submitted 1998 Thermal Blowup in Oligomeric solvents and Boger Fluids. ... 

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