In SPH two forms of artificial viscosity is necessary, the bulk and von Neumann-Richtmeyer viscosity. The standard recipy does however induce smoothening of the velocity differences and heating of the gas. Another problem is that standard artificial viscosity prevents compression of a gas.
To partly overcome some of these problems, I propose a modification of the artificial viscosity. The von Neumann-Richtmeyer artificial viscosity is used only in supersonic regions
where the gas is not under compression. The bulk viscosity is modified to be calculated from an integrated mean of the velocities in the neighbourhood of the particle, instead of calculating the viscous interaction from each neighbour separately. Tests cases have been performed to test these abilitites of the proposed modified form of artificial viscosity, and to compare them with standard artificial viscosity.
© European Southern Observatory (ESO) 1997
Online publication: April 28, 1998