The present work numerically investigates the performance aspects of a canonical diffuser geometry and the effect of turbulence as a possible parameter to control separation. A numerical model is developed in Ansys FLUENT and validated with the results of an experimental data set. The internal flow field is simulated for different inlet turbulence intensities and expansion ratios. The results show that turbulence intensity is proportional to the pressure recovery up to a maximum limit beyond which there is no more variation. Pressure recovery reaches a maximum up to an AR of 2.1 beyond which it starts falling rapidly. Numerical investigations using the RANS model on a 3D geometry show less pressure rise than experimental results.