  In this paper, we investigate the hemodynamics of a left atrium (LA) by
proposing a computational model suitable to provide physically meaningful fluid
dynamics indications and detailed blood flow characterization. In particular,
we consider the incompressible Navier-Stokes equations in Arbitrary Lagrangian
Eulerian (ALE) formulation to deal with the LA domain under prescribed motion.
A Variational Multiscale (VMS) method is adopted to obtain a stable formulation
of the Navier-Stokes equations discretized by means of the Finite Element
method and to account for turbulence modeling based on Large Eddy Simulation
(LES). The aim of this paper is twofold: on one hand to improve the general
understanding of blood flow in the human LA in normal conditions; on the other,
to analyse the effects of the turbulence VMS-LES method on a situation of blood
flow which is neither laminar, nor fully turbulent, but rather transitional as
in LA. Our results suggest that if relatively coarse meshes are adopted, the
additional stabilization terms introduced by the VMS-LES method allow to better
predict transitional effects and cycle-to-cycle blood flow variations than the
standard SUPG stabilization method.
