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Spurious currents in finite element based level set methods for two-phase flow
KTH, School of Computer Science and Communication (CSC), Numerical Analysis, NA.ORCID iD: 0000-0002-4911-467X
Uppsala Univ, Uppsala, Sweden .
Uppsala University.
2011 (English)In: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 69, no 9, 1433-1456 p.Article in journal (Refereed) Published
Abstract [en]

A study of spurious currents in continuous finite element based simulations of the incompressible Navier-Stokes equations for two-phase flows is presented on the basis of computations on a circular drop in equilibrium. The conservative and the standard level set methods are used. It is shown that a sharp surface tension force, expressed as a line integral along the interface, can give rise to large spurious currents and oscillations in the pressure that do not decrease with mesh refinement. If instead a regularized surface tension representation is used, exact force balance at the interface is possible, both for a fully coupled discretization approach and for a fractional step projection method. However, the numerical curvature calculation introduces errors that cause spurious currents. Different ways to extend the curvature from the interface to the whole domain are discussed and investigated. The impact of using different finite element spaces and stabilization methods is also considered.

Place, publisher, year, edition, pages
2011. Vol. 69, no 9, 1433-1456 p.
Keyword [en]
Curvature calculation, Finite element methods, Level set method, Spurious currents, Surface tension, Two phase flow
National Category
Computational Mathematics
URN: urn:nbn:se:kth:diva-33108DOI: 10.1002/fld.2643ISI: 000305450000001ScopusID: 2-s2.0-84862622190OAI: diva2:413363

QC 20120716

Available from: 2011-04-28 Created: 2011-04-28 Last updated: 2012-07-16Bibliographically approved
In thesis
1. Numerical Methods for Fluid Interface Problems
Open this publication in new window or tab >>Numerical Methods for Fluid Interface Problems
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns numerical techniques for two phase flowsimulations; the two phases are immiscible and incompressible fluids. Strategies for accurate simulations are suggested. In particular, accurate approximations of the weakly discontinuousvelocity field, the discontinuous pressure, and the surface tension force and a new model for simulations of contact line dynamics are proposed.

In two phase flow problems discontinuities arise in the pressure and the gradient of the velocity field due to surface tension forces and differences in the fluids' viscosity. In this thesis, a new finite element method which allows for discontinuities along an interface that can be arbitrarily located with respect to the mesh is presented. Using standard linear finite elements, the method is for an elliptic PDE proven to have optimal convergence order and a system matrix with condition number bounded independently of the position of the interface.The new finite element method is extended to the incompressible Stokes equations for two fluid systemsand enables accurate approximations of the weakly discontinuous velocity field and the discontinuous pressure.

An alternative way to handle discontinuities is regularization. In this thesis, consistent regularizations of Dirac delta functions with support on interfaces are proposed. These regularized delta functions make it easy to approximate surface tension forces in level set methods.

A new model for simulating contact line dynamics is also proposed. Capillary dominated flows are considered and it is assumed that contact line movement is driven by the deviation of the contact angle from its static value. This idea is used together with the conservative level set method. The need for fluid slip at the boundary is eliminated by providing a diffusive mechanism for contact line movement. Numerical experiments in two space dimensions show that the method is able to qualitatively correctly capture contact line dynamics.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011
Trita-CSC-A, ISSN 1653-5723 ; 2011:07
National Category
Computational Mathematics
urn:nbn:se:kth:diva-33111 (URN)978-91-7415-969-1 (ISBN)
Public defence
2011-05-20, Sal D3, Lindstedtsvägen 5, KTH, Stockholm, 14:21 (English)
Swedish e‐Science Research Center
QC 20110503Available from: 2011-05-03 Created: 2011-04-28 Last updated: 2012-05-24Bibliographically approved

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