On sharp surface force model: Effect of sharpening coefficient
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Vol. 2, No. 4, 2020, 00–00 https:// doi.org/10.1007/s42757-020-0063-5
On sharp surface force model: Effect of sharpening coefficient Kurian J. Vachaparambil (), Kristian Etienne Einarsrud Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
Abstract
Keywords
Amongst the multitude of approaches available in literature to reduce spurious velocities in
OpenFOAM®
Volume of Fluid approach, the Sharp Surface Force (SSF) model is increasingly being used due to its relative ease to implement. The SSF approach relies on a user-defined parameter, the sharpening coefficient, which determines the extent of the smeared nature of interface used to
spurious velocities two-phase flows Volume of Fluid
determine the surface tension force. In this paper, we use the SSF model implemented in OpenFOAM® to investigate the effect of this sharpening coefficient on spurious velocities and accuracy of dynamic, i.e., capillary rise, and static bubble simulations. Results show that
Article History
increasing the sharpening coefficient generally reduces the spurious velocities in both static and
Revised: 6 March 2020
dynamic cases. Although static millimeter sized bubbles were simulated with the whole range of sharpening coefficients, sub-millimeter sized bubbles show nonphysical behavior for values
Accepted: 7 March 2020
larger than 0.3. The accuracy of the capillary rise simulations has been observed to change
Research Article
non-linearly with the sharpening coefficient. This work illustrates the importance of using an optimized value of the sharpening coefficient with respect to spurious velocities and accuracy of
© The Author(s) 2020
Received: 6 January 2020
the simulation.
1
Introduction
Modelling surface tension dominant multiphase flows is relevant in a multitude of industrial processes like lab-on-chip, atomization, and boiling. One of the main approach to capture the interface dynamics is the Volume of Fluid method which uses the advection of scalar volume fraction based on algebraic (interface compression) or geometric (piecewise linear interface calculation or PLIC) reconstruction algorithms in order to preserve the sharpness of interfacial region (Cifani et al., 2016). The VOF based solver available in OpenFOAM, interFoam, which generates an interface which is smeared over a few computational cells uses the interface compression method due to its relative simplicity (Deshpande et al., 2012). In the VOF approach used in interFoam, the volume fraction field is used to determine curvature and corresponding surface tension force based on models like the widely used Continuum Surface Force (CSF) approach (Brackbill et al., 1992). Due to the smeared nature of the interface, the curvature and the pressure jump across the interface obtained from the simulations do not match the theoretical value which generates spurious velocities [email protected], [email protected]
(Deshpande et al., 2012).These spurious velocities introduce n
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