A new Partially Averaged Navier-Stokes (PANS) model is proposed with the aim of simulating unsteady separated flows at reasonable computational expense. The unresolved-to-total ratio of kinetic energy (fk) related to PANS method is taken as a spatially varying and dynamically updating parameter in the computations. Turbulent flow past a backward-facing step is chosen as a test case in an effort to evaluate the model performance. PANS computations are compared to the experimental data and the traditional Detached Eddy Simulations (DES), showing their excellent capability of resolving turbulent fluctuations. Boundary layer shielding technique is also introduced into the PANS approach and effectively improves the computational results.
