Simulation of fluid flow in intermeshing co-rotating twin-screw
extruders
Citation for published version (APA):
Sarhangi Fard, A., Anderson, P. D., Hulsen, M. A., & Meijer, H. E. H. (2009). Simulation of fluid flow in intermeshing co-rotating twin-screw extruders. Poster session presented at Mate Poster Award 2009 : 14th Annual Poster Contest.
Document status and date: Published: 01/01/2009 Document Version:
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Polymer Technology
Simulation of fluid flow in
intermesh-ing co-rotatintermesh-ing twin-screw extruders
A. Sarhangi Fard, P. D. Anderson, M. A. Hulsen, H. E. H. Meijer
/department of mechanical engineering
Introduction
Simulation of flow behaviour in twin screw extruders (TSE), has gained great endeavors in the past decades due to change of geometry with screw rotation and present of narrow gap region. Fictitious domain method (FDM) is used to avoid re-meshing. But the accuracy of FDM is not good enough particularly in the gap regions (Fig. 1) with high shear rates. For mixing analysis the accuracy of velocity field in the highly shear rate regions is essential.
screw-screw gap screw-barrel gap
2D cross-section
Fig. 1Cross section geometry of self-whipping co-rotating twin screw
extruder with narrow gaps between screw-screw and screw-barrel.
Objective
Using non-conforming mesh refinement extended finite element method (XFEM) to capture discontinuity of field variables across the solid-fluid interface and high shear rate regions.
Methods
The non-conforming mesh refinement technique is based on one fixed reference mesh where the quality of the refined mesh preserved [1]. To ensure the continuity across non-conforming regions a Lagrangian multiplier as constraint is imposed (Fig. 2).
Fig. 2Example of a finite element mesh used for FDM with
different mesh refinement scheme.
× × × × × × × × + Ω − Ω 1 e 2 e 3 e 4 e (a) (b)
Fig. 3 XFEM:(a) Non-intersected elements fully inside Ω+ are fully
integrated, intersected elements (gray color) are integrated on the inside part (Ω+
) and the elements (×) fully outside (Ω−) are ignored. (b) Subdivision of elements for integration.
We used XFEM to decouple the fluid and internal moving rigid bodies [2]. With XFEM the discontinuities of physical variables are captured using virtual degree of freedom as enrichment and applying special integration scheme over the intersected elements by rigid body (Fig. 3).
Results
Cross-section of twin screw extruder is selected as test case study geometry. We compared non-conforming FDM and XFEM re-sults with boundary fitted mesh (Fig. 4).
−0.80 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 4 8 12 16 20 23 BF X F θ=112.5 x=15.177 mm y/Rb V /V p −0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 −10 −5 0 5 10 15 F BF X θ=112.5 x=15.177 mm p y/Rb (a) (b)
Fig. 4(a) Tangential velocity (V /Vp) and (b) pressure (p) as a
func-tion of y/Rb over the line x = 15.177 mm, XFEM (X), boundary
fitted (BF) and FDM with high order refinement (F), Rb is barrel
radius.
In the gap region the XFEM shows much accurate result than FDM and it predicts the high value of velocity in y direction as same as BF result. We applied our method for 3D geometry of TSE (Fig. 5).
-120 -100-80 -60-40 -20 0 20 40 60 80 100
(a) (b)
Fig. 5(a) Contour plot of velocity at x direction for 3D conveying
element, (b) particle tracking.
Conclusion
Introducing modified techniques based on the mortar element, FDM and XFEM to simulate the fluid flow inside 3D geometry of TSE with narrow gaps and compare these methods.
References:
[1] Sarhangi Fard, A., Famili, N. and Anderson, P. D.: J. Com-puters and Chemical Engineering, 2007, 32, 1471-1481.
[2] Gerstenberger, A. and Wall, W. A.: Computer Methods in Ap-plied Mechanics and Engineering, 2008, 197, 1699-1714.
