Purpose - To perform 3D unsteady Reynolds Averaged Navier-Stokes (URANS) simulations to predict turbulent flow over bluff body. Design/methodology/ approach - Turbulence closure is achieved through a non-linear k-ε model. This model is incorporated in commercial FLUENT software, through user defined functions (UDF). Findings - The study shows that the present URANS with standard wall functions predicts all the major unsteady phenomena, with a good improvement over other URANS reported so far, which incorporate linear eddy viscosity models. The results are also comparable with those obtained by LES for the same test case. Originality/value - When comparing the computational time required by the present model and by LES, the accuracy achieved is significant and can be used for simulating 3D unsteady complex engineering flows with reasonable success. © Emerald Group Publishing Limited.