- Springer International Publishing Switzerland 2015. The objective of this study is to investigate the separation of a turbulent flow over smooth surfaces using the Partially Averaged Navier Stokes (PANS) Methodology. The degree of resolution in PANS, which can range from fully resolved to fully modeled turbulence, is parametrized by the ratio of modeled to resolved kinetic energy and dissipation. The flow geometry considered in this study consists of a channel constricted by a series of periodic hills which are spaced 9 hill heights apart from each other. This configuration yields flow separation over a curved surface with well defined flow conditions which makes it ideal as a benchmark case for turbulence closure model validation. Flow Reynolds number based on the bulk velocity above the crest of the hill and hill height is 37,000. Several PANS simulations are performed to study the effect of cut-off length scale and grid size. Turbulence statistics such as averaged mean velocity and Reynolds stresses are compared against well documented experimental and numerical data.