a) tsim = 3 s (b) tsim = 16 s (c) tsim = 16 s (detergent in blue) Figure 1: The pan's surface is cleansed from grease (orange) due to detergent concentration (blue in 1(c)) on the fluid's surface. AbstractSurface effects play an essential role in fluid simulations. A vast number of dynamics including wetting of surfaces, cleansing, and foam dynamics are based on surface-surface and surface-bulk interactions, which in turn rely on a robust surface computation. In this paper we introduce a conservative Lagrangian formulation of surface effects based upon incompressible smoothed particle hydrodynamics (SPH). The key concept of our approach is to realize an implicit definition of the fluid's (free) surface by assigning each particle a value estimating its surface area. Based on this consistent surface representation, a conservative coupling of bulk and surface is achieved. We demonstrate the applicability and robustness of our approach for several types of surface-relevant effects including adsorption, diffusion and reaction kinetics.

We present a physically-based multiphase model for simulating water and air bubbles with Smoothed Particle Hydrodynamics (SPH). Since the high density ratio of air and water is problematic for existing SPH solvers, we compute the density and pressure forces of both phases separately. The two-way coupling is computed according to the velocity field. The proposed model is capable of simulating the complex bubble flow, e. g. path instability, deformation and merging of bubbles and volume-dependent buoyancy. Furthermore, we present a velocity-based heuristic for generating bubbles in regions where air is likely trapped. Thereby, bubbles are generated on the fly, without explicitly simulating the air phase surrounding the liquid. Instead of deleting the bubbles when they reach the surface, we employ a simple foam model. By incorporating our model into the predictive-corrective SPH method, large time steps can be used. Thus, we can simulate scenarios of high resolution where the size of the bubbles is small in comparison to the liquid volume.

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