Abstract
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 ([Formula: see text]), 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.
Highlights
Adding polymer or some certain surfactant into water or other Newtonian fluid, the solution has the behaviors of both viscous Newtonian fluid and elastic solid simultaneously and is called viscoelastic fluid
Numerical simulations are performed on the flow through sudden expansion geometry for Newtonian fluid at different Reynolds numbers, while, for viscoelastic fluid, three more parameters, Weissenberg number, concentration (measured by the solvent viscosity ratio defined as β = μs/(μs + μp)), and extensibility parameters (L2), are taken into consideration
In order to study the effect induced by elasticity, extensibility, concentration, and inertia on the sudden expansion flow, numerical simulations are systematically conducted on viscoelastic fluid flows through sudden expansion geometry at different Weissenberg numbers, extensibility parameters, solvent viscosity ratios, and Reynolds numbers, respectively
Summary
Adding polymer or some certain surfactant into water or other Newtonian fluid, the solution has the behaviors of both viscous Newtonian fluid and elastic solid simultaneously and is called viscoelastic fluid. The presence of elasticity brings viscoelastic fluid special rheological characteristics which are different from those of Newtonian fluid, such as shear thinning in viscosity, nonzero normal stress difference, Weissenberg effect (rod-climbing), extrusion swell, tubeless siphon, elastic recoil [1], and turbulent drag reduction effect [2,3,4,5,6,7]. Among these characteristics, turbulent drag reduction is an exciting phenomenon and has great potential in energy saving for industrial application systems. Before the development of subroutine modeling turbulent flow for the step, the established viscoelastic fluid subroutine for laminar flow without consideration of turbulence modeling needs to be benchmarked, which is the purpose of the present paper
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