Real-Time Fluid Simulation with Atmospheric Pressure Using Weak Air Particles

Atmospheric pressure is important yet often ignored in fluid simulation, resulting in many phenomena being overlooked. This paper presents a particle-based approach to simulate versatile liquid effects under atmospheric pressure in real time. We introduce weak air particles as a sparse sampling of air. The weak air particles can be used to efficiently track liquid surfaces under atmospheric pressure, and are weakly coupled with the liquid. We allow the large-mass liquid particles to contribute to the density estimation of small-mass air particles and neglect the air's influence on liquid density, leaving only the surface forces of air on the liquid to guarantee the stability of the two-phase flow with a large density ratio. The proposed surface force model is composed of density-related atmospheric pressure force and surface tension force. By correlating the pressure and the density, we ensure that the atmospheric pressure increases as the air is compressed in a confined space. Experimental results demonstrate the efficiency and effectiveness of our methods in simulating the interplay between air and liquid in real time.