Well working hydraulic systems need clean hydraulic oil. Therefore, the system must ensure the separation of molecular, gaseous, liquid and solid contaminations. The key element of the separation of contaminants is the hydraulic reservoir. Solid particles are a major source of maintenance costs and machine downtime. Thus, an Euler-Euler-Lagrange multiphase CFD model to predict the transport of solid particles in hydraulic reservoirs was developed. The CFD model identifies and predicts the particle accumulation areas and is used to train port-to-port transfer functions, which can be used in system models to simulate the long-term contamination levels of hydraulic systems. The experimental detection of dynamic particle contamination levels and particle accumulation areas validate and confirm the CFD and the system model. Both models in combination allow for parameter and design studies to improve the fluid management of hydraulic reservoirs.