An Approach to Solve the Difficulties in the SPH Modeling of Viscous and Free-Boundary Layers

Adaptive interpolation spatial domains have been widely used with the aim of performing better spatial interpolations in Smooth Particle Hydrodynamics (SPH), mainly for expanding or shock gas dynamics. A transport phenomenology, applied to a low compressibility gas inside a definite potential well for accretion disc modeling in close binaries, represents a significant numerical test to check adaptive SPH (ASPH) reliability. Well-bound disc structures do not come out as viscous structures in ASPH modeling, whichever is the adopted interpolation Kernel. Therefore, ASPH lack in reproducing well-bound low compressibility viscous disc structures where the gas geometric edges are free boundaries (FB) towards the empty free space. Gaussian Kernels without any spatial radial restriction, whose half width at half maximum (HWHM) is constant, can be rightly adopted in such troublesome physical regimes. Therefore, a Gaussian SPH in extended particle range (GASPRER) gives more significant results.