  In this paper, the Immersed Boundary Method (IBM) proposed by Pinelli is
implemented for finite volume approximations of incompressible Navier-Stokes
equations solutions in the open source toolbox OpenFOAM version 2.2. Solid
obstacles are described using a discrete forcing approach for boundary
conditions. Unlike traditional approaches encompassing the presence of a solid
body using conformal meshes and imposing no-slip boundary conditions on the
boundary faces of the mesh, the solid body is here represented on the Eulerian
Cartesian mesh through an ad-hoc body force evaluated on a set of Lagrangian
markers. The markers can move across the Eulerian mesh, hence allowing for a
straightforward analysis of motion or deformation of the body. The IBM method
is described and implemented in PisoFOAM, whose Pressure-Implicit
Split-Operator (PISO) solver is modified accordingly. The presence of the solid
body and the divergence-free of the fluid velocity are imposed simultaneously
by sub-iterating between IBM and the pressure correction step. This scheme
allows for the use of fast optimized Poisson solvers while granting excellent
accuracy with respect to the previously mentioned constraints. Various 2D and
3D well-documented test cases of flows around fixed or moving circular
cylinders are simulated and carefully validated against existing data from the
literature. The capability of the new solver is discussed in terms of accuracy
and numerical performances.
