Internally in the solvers, during a co-simulation, the simulations are coupled through walls. The walls of the particle solver model are barriers that the particles cannot pass through. The particles apply forces to the walls either as contact forces or pressures. Some or all of the walls of a particle model will be connected to bodies in the RecurDyn model. When a body that is connected to a wall moves in RecurDyn, the connected wall moves in the particle solver. When the particles apply a contact or pressure force to a wall in the particle solvers, the force is applied to the body in RecurDyn. This couples the dynamics of both the system of RecurDyn bodies and the system of particles in the particle solver to create an accurate multi-physics simulation.
RecurDyn uses the RecurDyn Standard Particle Interface (SPI) to accomplish co-simulation with particle solvers. The RecurDyn SPI is an API that a particle solver can support. If a particle solver has implemented support for the RecurDyn SPI, then the particle solver can co-simulate with RecurDyn.