title: Liquid drops and surface tension with smoothed particle applied mechanics
abstract: Smoothed particle applied mechanics (SPAM), also referred to as smoothed particle hydrodynamics, is a Lagrangian particle method for the simulation of continuous flows. Here we apply it to the formation of a liquid drop, surrounded by its vapor, for a van der Waals (vdW) fluid in two dimensions. The cohesive pressure of the vdW equation of state gives rise to an attractive, central force between the particles with an interaction range which is assumed to exceed the interaction range of all the other smoothed forces in the SPAM equations of motion. With this assumption, stable drops are formed, and the vdW phase diagram is well reproduced by the simulations. Below the critical temperature, the surface tension for equilibrated drops may be computed from the pressure excess in their centers. It agrees very well with the surface tension independently determined from the vibrational frequency of weakly excited drops. We also study strongly deformed drops performing large-amplitude oscillations, which are reminiscent of the oscillations of a large ball of water under microgravity conditions. In an appendix we comment on the limitations of SPAM by studying the violation of angular momentum conservation, which is a consequence of noncentral forces contributed by the full Newtonian viscous stress tensor.
authors.affiliation: Institut fur Experimentalphysik, Universitat Wien, Boltzmanngasse 5, A-1090 Wien, Austria.
authors.initials: S
authors.lastname: Nugent
authors.initials: HA
authors.lastname: Posch