On vortex development in viscoelastic expansion and contraction flows

Baloch, A.; Townsend, Peter; Webster, M.F.

doi:10.1016/0377-0257(96)01470-x

Cited by 63 publications

(31 citation statements)

References 17 publications

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“…2. Vortex sizes and intensities are smaller for the viscoelastic liquid, compared with the Newtonian, a finding also reported in previous studies under different conditions [4,5,8]. This effect is observed for the whole range of Re, from 0 to 100 (the exception being the size of the smaller vortex X r2 which is actually larger for the non-Newtonian fluid) and can be seen as a swelling-like phenomenon similar to that occurring in extrusion processes.…”

Section: Effect Of Inertia Resupporting

confidence: 82%

“…Compared with other works, the present level of mesh refinement is similar to that used by Hawa and Rusak [13] (their base mesh had δx = 0.05) who solved the Newtonian problem with a vorticity/stream function formulation using a finite-difference method; in relation to works dealing with viscoelastic flow simulations in planar expansions at very low Re, Mesh-2 is much finer than those previously used [5,7,8]. Numerical accuracy was assessed for both Newtonian and viscoelastic fluids with a Reynolds number of 60, in the middle of the range here considered (Re = 0.01-100) but for which the flow is already asymmetric for both fluid types.…”

Section: Meshes and Quantification Of Accuracymentioning

confidence: 88%

“…For the case which could be considered as two-dimensional, with an expansion ratio of 3:40 (E ≡ D/d = 13.3), the Reynolds number covered were too low (Re ≤ 7) for the observation of any steady asymmetric flow pattern. Later, Baloch et al [5,6] simulated some of the experimental cases in [4] by using again the linear form of the Phan-Thien/Tanner model; these simulations were restricted to high expansion ratios and low Reynolds numbers (Re ≤ 4). No attempt was made to capture flow asymmetries.…”

Section: Introductionmentioning

confidence: 99%

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Asymmetric flows of viscoelastic fluids in symmetric planar expansion geometries

Oliveira

2003

Journal of Non-Newtonian Fluid Mechanics

110

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The flow of viscoelastic liquids with constant shear viscosity through symmetric sudden expansions is studied by numerical means. The geometry considered is planar and the constitutive model follows the modified FENE-CR equation, valid for relative dilute solutions of polymeric fluids. For Newtonian liquids in a 1:3 expansion we predict the result that the flow becomes asymmetric for a Reynolds number (based on upstream mean velocity and channel height) of about 54, in agreement with previously published results. For the non-Newtonian case the transition depends on both the concentration and the extensibility parameters of the model, and the trend is for the pitch-fork bifurcation to occur at higher Reynolds numbers. Detailed simulations are carried out for increasing Reynolds number, at fixed concentration and Weissenberg number, and for increasing concentration at a fixed Reynolds number of 60. The results given comprise size and strength of the recirculation zones, bifurcation diagrams, and streamline plots.

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Section: Effect Of Inertia Resupporting

confidence: 82%

Section: Meshes and Quantification Of Accuracymentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Asymmetric flows of viscoelastic fluids in symmetric planar expansion geometries

Oliveira

2003

Journal of Non-Newtonian Fluid Mechanics

110

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“…Indeed, it has been found (Quinzani, Armstrong & Brown 1995) to be the best simple differential model to represent the elongational properties of polymer solutions in entry flows. For example, both Baaijens (1993) and Azaiez Guénette & Aït-Kadi (1996) have used the linearized form to predict the entry flow through the 4 : 1 planar contraction measured by Quinzani et al (1995); Baloch, Townsend & Webster (1996) have also used it to simulate both expansion and contraction flows. The exponential form of the PTT model gives a maximum of the elongational viscosity at a given level of strain rate in simple stretching flows, as is typical of some polymer melts; it was used, for example, by White & Baird (1988a, b) to simulate their own measurements.…”

Section: Introductionmentioning

confidence: 99%

Analytical solution for fully developed channel and pipe flow of Phan-Thien–Tanner fluids

1999

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Analytical expressions are derived for the velocity vector, the stress components and the viscosity function in fully developed channel and pipe flow of Phan-ThienTanner (PTT) fluids; both the linearized and the exponential forms of the PTT equation are considered. The solution shows that the wall shear stress of a PTT fluid is substantially smaller than the corresponding value for a Newtonian or upperconvected Maxwell fluid, with implications for comparing predicted and measured values in a non-dimensional form.

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“…Flows through two-dimensional expansion with expansion ratio of 3 : 40 at low Reynolds number were simulated for comparison with some cases in their experiments, and satisfactory agreement was obtained. Baloch et al [12] used the same method and viscoelastic constitutive model as used in Townsend and Walters [11] to simulate the two-dimensional expansion flows with expansion ratios of 3 : 40 and 1 : 80 at low Reynolds numbers (Re ≤ 4). The results for the flows with expansion ratio of 3 : 40 showed good qualitative agreement with some experimental cases conducted by Townsend and Walters [11].…”

Section: Introductionmentioning

confidence: 99%

Modeling Asymmetric Flow of Viscoelastic Fluid in Symmetric Planar Sudden Expansion Geometry Based on User-Defined Function in FLUENT CFD Package

Zheng

Yang

2013

Advances in Mechanical Engineering

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Through embedding an in-house subroutine into FLUENT code by utilizing the functionalization of user-defined function provided by the software, a new numerical simulation methodology on viscoelastic fluid flows has been established. In order to benchmark this methodology, numerical simulations under different viscoelastic fluid solution concentrations (with solvent viscosity ratio varied from 0.2 to 0.9), extensibility parameters (100 ≤ 2 ≤ 500), Reynolds numbers (0.1 ≤ Re ≤ 100), and Weissenberg numbers (0 ≤ Wi ≤ 20) are conducted on unsteady laminar flows through a symmetric planar sudden expansion with expansion ratio of 1 : 3 for viscoelastic fluid flows. The constitutive model used to describe the viscoelastic effect of viscoelastic fluid flow is FENE-P (finitely extensive nonlinear elastic-Peterlin) model. The numerical simulation results show that the influences of elasticity, inertia, and concentration on the flow bifurcation characteristics are more significant than those of extensibility. The present simulation results including the critical Reynolds number for which the flow becomes asymmetric, vortex size, bifurcation diagram, velocity distribution, streamline, and pressure loss show good agreements with some published results. That means the newly established method based on FLUENT software platform for simulating peculiar flow behaviors of viscoelastic fluid is credible and suitable for the study of viscoelastic fluid flows.

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On vortex development in viscoelastic expansion and contraction flows

Cited by 63 publications

References 17 publications

Asymmetric flows of viscoelastic fluids in symmetric planar expansion geometries

Asymmetric flows of viscoelastic fluids in symmetric planar expansion geometries

Analytical solution for fully developed channel and pipe flow of Phan-Thien–Tanner fluids

Modeling Asymmetric Flow of Viscoelastic Fluid in Symmetric Planar Sudden Expansion Geometry Based on User-Defined Function in FLUENT CFD Package

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