A validation study for two CFD models of the timevarying flow through a confined bank of cylinders is presented. The facility mimics the lower plenum of a high temperature reactor and is arranged with the cylinders on equilateral triangles with pitch to diameter ratio of 1.7. Time-resolved Particle Image Velocimetry (PIV) measurement coupled with pressure measurements along the facilities walls are compared to both the Unsteady Reynolds Averaged Navier Stokes (URANS) kωw model and the Detached Eddy Simulation (DES) models. Spatial (i.e. timeaveraged bulk velocity and pressure losses and local velocity distributions) and temporal (i.e. dominant frequencies and correlations) validation parameters on both the local and global scale are used for validation. It is found the CFD models accurately predict frequencies present in the pressure along the walls next to the cylinders in the first and the last cylinder, yet predicts other dominant frequencies in the remaining cylinders that are not found in the experiment. The temporal behavior of the DES was generally far superior to that of the URANS model.