This research paper compared three k-ε family turbulence models; Standard k-ε, RNG k-ε and Realizable k-ε, and two k-ɷ family models; Standard k-ɷ and Stress-Strain Transport, SST k-ɷ. The turbulent flow characteristics were predicted in a two-dimensional of 10° half-angle diffuser using the five turbulence models with the ANSYS FLUENT 13.0 code. Numerical results were validated by comparing them to experimental fluid dynamics (EFD) results. Velocity profiles, turbulent kinetic energy profiles and skin friction coefficients were presented validate the numerical results. Contours velocity-streams functions were shown as well. One of the most interesting observations of comparing numerical solutions to EFD data was apparently that k-ε family models have a valid prediction of flow characteristics that are far away from wall effects, however, k-ɷ models have a significant prediction of flow behavior nearby the wall boundaries. In addition, the changes in the quality of meshing elements and its number have noticeable influences on computational fluid dynamics (CFD) results. Personally, the present CFD investigation obviously has given a deep insight of the most important fluid dynamics concepts that were studied in the computational fluid dynamics course
