Incompressible sph method for simulating newtonian and non-newtonian flows with a free surface
Cites background from "Incompressible sph method for simul..."
...They are regularly distributed at the initial state and have zero velocity through the whole simulation, while several layers of dummy particles  are built as an extension of the edge particles surrounding the solid boundaries to ensure the same order of discretisation (in terms of kernel compact support) for particles located close to those boundaries, as for particles located in the core of the domain....
...There are several ways to prevent this phenomenon, for example, by using mirror particles  or some repulsive forces , or dummy particles ....
Cites methods from "Incompressible sph method for simul..."
...The method of Shao and Lo , although stable, is quite noisy and inaccurate....
...This instability has been avoided in various ways: by imposing invariant density rather than zero velocity divergence , by imposing zero velocity divergence and density invariance together , and by imposing the kinematic constraint of constant volume for each particle through non-thermodynamic pressure ....