Two-way coupling of fluids to rigid and deformable solids and shells

Abstract

Figure 1: (Left) Many rigid balls with varying densities plunge into a pool of water. (Center) Water splashes out of an elastic cloth bag. (Right) A balloon shoots upwards, releasing a jet of smoke. AbstractWe propose a novel solid/fluid coupling method that treats the coupled system in a fully implicit manner making it stable for arbitrary time steps, large density ratios, etc. In contrast to previous work in computer graphics, we derive our method using a simple back-ofthe-envelope approach which lumps the solid and fluid momenta together, and which we show exactly conserves the momentum of the coupled system. Notably, our method uses the standard Cartesian fluid discretization and does not require (moving) conforming tetrahedral meshes or ALE frameworks. Furthermore, we use a standard Lagrangian framework for the solid, thus supporting arbitrary solid constitutive models, both implicit and explicit time integration, etc. The method is quite general, working for smoke, water, and multiphase fluids as well as both rigid and deformable solids, and both volumes and thin shells. Rigid shells and cloth are handled automatically without special treatment, and we support fully one-sided discretizations without leaking. Our equations are fully symmetric, allowing for the use of fast solvers, which is a natural result of properly conserving momentum. Finally, for simple explicit time integration of rigid bodies, we show that our equations reduce to a form similar to previous work via a single block Gaussian elimination operation, but that this approach scales poorly, i.e. as though in four spatial dimensions rather than three.

Physical simulation of wet clothing for virtual humans

“…Robinson-Mosher et al [11] studied the cloth-fluid interface through two-way interaction conserving momentum and constraining the surface boundary. This work focuses on the surface interaction of cloth and fluid.…”

Controlling shapes of air bubbles in a multi-phase fluid simulation

“…Hong and Kim [11] considered surface tension between multi-phase fluids using the ghost fluid method (GFM) to deal with discontinuities at the fluid surface. Robinson-Mosher et al introduced interactions between rigid bodies and a fluid [23]. Hong and Kim [10] and Shin and Kim [24] controlled the shape of a fluid using a gradient-based non-linear method, and Shi and Yu [27] introduced a target-driven method to force fluids to follow a rapidly deforming target shape.…”

Fluid simulation with adaptively sharpening and embedded boundary conditions

“…Full simultaneous coupling between fluid and solid was achieved by Klingner et al [21] and Chentanez et al [26]. Later on, Batty et al [27] introduced the fast and robust variational framework and Robinson-Mosher et al [28] used the "back-of-the-envelope" method to achieve higher accuracy and better performance. By the way, the Lattice Boltzmann method (LBM) in computer graphics is becoming popular as it can naturally handle some problem difficult for the classical Euler and Lagrangian methods.…”