# Artificial Viscosity

^{1}implementations, viscosity is rather an inter-particles pressure than a bulk pressure. It was shown that the use of Equation 1 and Equation 2 generates a substantial amount of entropy in regions of strong shear even if there is no compression.

^{2}The artificial viscosity is decreased in regions where vorticity is high with respect to velocity divergence.

Default values for ${q}_{a}$ and ${q}_{b}$ are respectively set to 2 and 1.

^{1}Monaghan J.J., “Smoothed Particle Hydrodynamics”, Annu.Rev.Astron.Astro-phys; Vol. 30; pp. 543-574, 1992.

^{2}Balsara D.S., “Von Neumann Stability Analysis of Smoothed Particle Hydrodynamics Suggestions for Optimal Algorithms”, Journal of Computational Physics, Vol. 121, pp. 357-372, 1995.