The Reduced Immersed Method for Real-Time Fluid-Elastic Solid Interaction and Contact Simulation

Christopher Brandt, Leonardo Scandolo, Elmar Eisemann, Klaus Hildebrandt

We introduce the Reduced Immersed Method (RIM) for the real-time simu-lation of two-way coupled incompressible fluids and elastic solids and theinteraction of multiple deformables with (self-)collisions. Our framework isbased on a novel discretization of theimmersed boundary equations of motion,which model fluid and deformables as a single incompressible medium andtheir interaction as a unified system on a fixed domain combining Eulerianand Lagrangian terms. One advantage for real-time simulations resultingfrom this modeling is that two-way coupling phenomena can be faithfullysimulated while avoiding costly calculations such as tracking the deform-ing fluid-solid interfaces and the associated fluid boundary conditions. Ourdiscretization enables the combination of a PIC/FLIP fluid solver with areduced-order Lagrangian elasticity solver. Crucial for the performance ofRIM is the efficient transfer of information between the elasticity and thefluid solver and the synchronization of the Lagrangian and Eulerian set-tings. We introduce the concept oftwin subspacesthat enables an efficientreduced-order modeling of the transfer. Our experiments demonstrate thatRIM handles complex meshes and highly resolved fluids for large time stepsat high framerates on off-the-shelf hardware, even in the presence of highvelocities and rapid user interaction. Furthermore, it extends reduced-orderelasticity solvers such as Hyper-Reduced Projective Dynamics with naturalcollision handling.

The Reduced Immersed Method for Real-Time Fluid-Elastic Solid Interaction and Contact Simulation