Enforcing boundary conditions in SPH applications involving bodies with right angles

The viscous flow around a moving square is characterized by the flow separation induced by the geometry of the body, and by the generation of strong vorticity associated with strong pressure gradients as shown by the reference results in the benchmark test n.6 [1]. The Lagrangian nature of SPH makes the modelling of these features very difficult even at low Reynolds numbers. This work analyzes the problems associated with the Lagrangian motion of the particles, and how they disappear in an "Eulerian" SPH formulation. The stiff problem of the Lagrangian motion of the particles around the corner is partially made milder by the use of a background pressure, an anti-clamping correction and the coupling with a local analytical solution.