A fictitious domain formulation for flows with rigid particles: A non-Lagrange multiplier version

In this paper, we present a development of the fictitious domain method proposed in Ref. [C. Diaz-Goano, P. Minev, K. Nandakumar, A fictitious domain/finite element method for particulate flows, J. Comput. Phys. 192 (2003) 105]. The main new feature of the modified method is that after a proper splitting, it avoids the need to use Lagrange multipliers for imposition of the rigid body motion and instead, it resolves the interaction force between the two phases explicitly. Then, the end-of-step fluid velocity is a solution of an integral equation. The most straightforward way to resolve it is via an iteration but a direct extrapolation is also possible. If the latter approach is applied then the fictitious domain formulation becomes fully explicit with respect to the rigid body constraint and therefore, the corresponding numerical procedure is much cheaper. Most of the numerical results presented in this article are obtained with such an explicit formulation.