Paul A. Taylor, John C. Miller
A commonly cited drawback of SPH is the introduction of spurious shear
viscosity by the artificial viscosity term in situations involving rotation.
Existing approaches for understanding its effect include approximative analytic
formulae and disc-averaged behaviour in specific ring-spreading simulations,
based on the kinematic contribution of the artificial viscosity. In this work,
we have developed a simple, general technique for evaluating the local effect
of artificial viscosity directly from the entropic function of each SPH
particle. This is simple and quick to implement, and it allows a detailed
characterization of its effects as a function of position. Several advantages
of this local method are discussed, including its ease in evaluation, its
greater accuracy and its broad applicability to arbitary flow geometries and
equations of state. Here, we apply this approach to various disc flows,
including simulations which implement the commonly-used Balsara switch.
Comparisons with existing analytic estimates are made, and examples of
quantifying explicit dependencies of the effective viscosity in terms of SPH
and flow parameters are given. Additionally, a method for the initial placement
of SPH particles which reduces numerical fluctuations is discussed and
utilised.
View original:
http://arxiv.org/abs/1112.5120
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