Adaptive particle refinement for compressible smoothed particle hydrodynamics

We introduce adaptive particle refinement for compressible smoothed particle hydrodynamics (SPH). SPH calculations have the natural advantage that resolution follows mass, but this is not always optimal. Our implementation allows the user to specify local regions of the simulation that can be more highly resolved. We test our implementation on practical applications including a circumbinary disc, a planet embedded in a disc and a flyby. By comparing with equivalent globally high resolution calculations we show that our method is accurate and fast, with errors in the mass accreted onto sinks of less than 9 percent and speed ups of 1.07-6.62 times for the examples shown. Our method is adaptable and easily extendable, for example with multiple refinement regions or derefinement.