Gasoline2: A Modern SPH Code
  The methods in the Gasoline2 Smoothed Particle Hydrodynamics (SPH) code are
described and tested. Gasoline2 is the most recent version of the Gasoline code
for parallel hydrodynamics and gravity with identical hydrodynamics to the
Changa code. As with other Modern SPH codes, we prevent sharp jumps in time
steps, use upgraded kernels and larger neighbour numbers and employ local
viscosity limiters. Unique features in Gasoline2 include its
Geometric-Density-Average Force expression, explicit Turbulent Diffusion terms
and Gradient-Based shock detection to limit artificial viscosity. This last
feature allows Gasoline2 to completely avoid artificial viscosity in
non-shocking compressive flows. We present a suite of tests demonstrating the
value of these features with the same code configuration and parameter choices
used for production simulations.
