Accurate Viscous Free Surfaces for
Buckling,
Coiling, and Rotating Liquids

A
stream of highly viscous liquid spontaneously coils and buckles due to the 
Abstract: We present a fully implicit Eulerian technique for simulating
free surface viscous liquids which eliminates artifacts in previous approaches,
efficiently supports variable viscosity, and allows the simulation of more
compelling viscous behaviour than previously achieved in graphics. Our method
exploits a variational principle which automatically enforces the complex
boundary condition on the shear stress at the free surface, while giving rise
to a simple discretization with a symmetric positive definite linear system. We
demonstrate examples of our technique capturing realistic buckling, folding and
coiling behavior. In addition, we explain how to handle domains whose boundary
comprises both ghost fluid Dirichlet and variational Neumann parts, allowing
correct behaviour at free surfaces and solid walls for both our viscous solve
and the variational pressure projection of [Batty et al. 2007].
Paper: PDF
Talk: Powerpoint
Video: Quicktime
Sample Code: Viscosity2D
A 2D implementation of our approach, built on top of a very simple free surface liquid simulator.
Authors:
Christopher Batty  University of
Robert Bridson 
Citation: C. Batty and R. Bridson. Accurate Viscous Free Surfaces for
Buckling, Coiling and Rotating Liquids. In Proceedings of ACM/Eurographics
Symposium on Computer Animation, 2008.
Bibtex:
@inproceedings{viscousFluid08,
author = {Christopher Batty and Robert Bridson},
title = {Accurate Viscous Free Surfaces for Buckling, Coiling, and Rotating Liquids},
booktitle = {Proceedings of the 2008 ACM/Eurographics Symposium on Computer Animation},
pages = {219228},
year = {2008},
month = {July},
}
Funding:
Natural Sciences and Engineering Research Council of Canada
Related Projects:
A
Fast Variational Framework for Accurate SolidFluid Coupling
This paper introduces the idea of using a variational principle in combination
with finite differences to easily capture a natural boundary condition using
volume fractions. In this case, it is the solid boundary condition for
pressure, whereas in the above paper the focus is on free surface boundary
conditions for viscosity.
As of this writing (Dec 2010) this technique is used in two commercial software products, DPIT EFFEX and Exotic Matter's Naiad.