Calibrating an updated smoothed particle hydrodynamics scheme within GCD

We adapt a modern scheme of smoothed particle hydrodynamics (SPH) to our tree N-body/SPH galactic chemodynamics code GCD+. The applied scheme includes implementations of the artificial viscosity switch and artificial thermal conductivity proposed by Morris & Monaghan, Rosswog & Price and Price to model discontinuities and Kelvin-Helmholtz instabilities more accurately. We first present hydrodynamics test simulations and contrast the results to runs undertaken without artificial viscosity switch or thermal conduction. In addition, we also explore the different levels of smoothing by adopting larger or smaller smoothing lengths, i.e. a larger or smaller number of neighbour particles, N-nb. We demonstrate that the new version of GCD+ is capable of modelling Kelvin-Helmholtz instabilities to a similar level as the mesh code, ATHENA. From the Gresho vortex, point-like explosion and self-similar collapse tests, we conclude that setting the smoothing length to keep N-nb as high as similar to 58 is preferable to adopting smaller smoothing lengths. We present our optimized parameter sets from the hydrodynamics tests.