Can we do it using overset meshing? I tried using overset meshing by created a small fluid domain around each of the cylinders and created a 6dof object for each cylinder providing mass and moment of inertia with respect to center of big cylinder. Initially, I tried with two small cylinders each on left and right side of big cylinder at the center. Whenever I press calculate, fluent closes abruptly throwing me "MPI Application rank 0 exited before MPI_Finalize() with status -1073741571.n