L'exploitation minière des sables bitumineux requiert une succession de nombreuses opérations pour séparer le bitume, l'eau et le sable. La séparation solide/liquide fait intervenir un hydrocyclone. Afin de limiter l'ajout d'eau, l'hydrocyclone doit fonctionner dans des conditions inhabituelles correspondant à une concentration élevée à l'alimentation. Une étude expérimentale a permis de caractériser l'ensemble des régimes de fonctionnement, l'influence de la concentration et des caractéristiques géométriques. De plus, des simulations numériques ont été réalisées avec NEPTUNE_CFD@Tlse. Deux méthodes sont proposées pour modéliser les comportements observés à faible et à forte concentration. Les résultats numériques sont en bon accord avec les expériences sur toute la gamme de concentration. L'étude des phénomènes locaux permet une meilleure compréhension des mécanismes de séparation. / Tar sands beneficiation requires a series of processing steps for separation of bitumen, water and sand particles. In this process, hydrocyclones are used to separate sand from water and bitumen, thereby recovering additional bitumen and concentrating sand particles before sending them off to tailing ponds. In order to reduce fresh water consumption (environmental policy), hydrocyclones need to operate with high feed solids content, say 50% in mass, which lays outside their standard operating regime. The response and performance of hydrocyclones need to be understood under such stringent operating conditions. A pilot scale experiment was commissioned for testing a 100mm diam. hydrocyclone under different operating regimes of discharge and measuring the corresponding separation performance. Feed solids concentration and geometrical properties were varied extensively. Separation performance indicators, including partition curve, cut-size, sharpness index and water recovery to underflow were obtained by standard data reconciliation. The experimental data provided all the information required to test the CFD model that was derived to simulate the hydrocyclone. Eulerian simulations of the three-dimensional liquid-solid flow inside the hydrocyclone were carried out, using a multi-fluid model (NEPTUNE_ CFD@Tlse). The actual geometrical features and operating conditions of the hydrocyclone were accurately matched in the simulations. Two simulation approaches have been proposed for hydrocyclone modelling, depending on their operating under dilute conditions, with a spray discharge or dense conditions, with a rope discharge. Numerical simulation results are in good agreement with experiments. Local analysis of hydrodynamic features yields new insights into the behaviour of hydrocyclones at high feed solids concentration.