EDF aims at identifying what causes fuel assembly vibrations in Pressurized Water Reactor (PWR). The present work focuses on the validation of pressure fluctuations along the central rod of a 5×5 configuration for wall-modelled Large Eddy Simulation (LES). New experiments, called CALIFS, have been carried out by CEA (Atomic Energy Commission) on a 5×5 Mixing Vane Grid (MVG) in the framework of “Fuel Assembly” EDF/CEA/FRAMATOME tripartite project. In addition to pressure drop and velocity measurements using Particle Image Velocimetry (PIV), pressure measurements have been performed along the central rod. The computational domain is representative of a span of the experimental mock-up, composed of a 5×5 rod bundle equipped with a split-type mixing vane grid. The hydraulic Reynolds number is equal to 66,000 and periodic boundary conditions are imposed in the stream-wise direction. The mesh is fully hexahedral and conformal. Computations give very satisfactory results for the pressure drop, the mean velocity and the Reynolds stresses at different locations. The r.m.s. of the pressure along the central rod is also compared to experimental data at different heights. The behavior is in very good agreement up to 5 hydraulic diameters downstream the mixing vane grid.