A Comparison of Unsteady RANS Simulations With PIV Data in an Axial Turbomachine

This paper presents a comparison of 2D unsteady Reynolds Averaged Navier-Stokes (RANS) simulations using two standard turbulence models, i.e. RNG k-ε and a Reynolds Stress Transport Model, with experimental data, obtained using two-dimensional Particle Image Velocimetry (PIV) measurements within an entire stage of an axial turbomachine. The computations are performed using the commercial flow solver FLUENT™. A sliding mesh interface between the rotor and stator domains is used. The PIV measurements are performed in a refractive-index-matched facility that provides unobstructed view, and cover the entire 2^nd stage of a two-stage axial pump. The inlet velocity and turbulence boundary conditions are provided from the experimental data. Detailed side-by-side comparisons of computed and measured phase-averaged velocity as well as turbulence fields within the entire stage are presented. Quantitative comparisons between the experiments and the computations are also included in terms of line distributions within the rotor-stator gap and the stator wake regions. The results show that, although there is reasonable agreement in general between the experimental results and the computational simulations, some critical flow features are not correctly predicted. The turbulent kinetic energy levels are generally too high in the simulations, with substantial amount of unphysical turbulence generation near the blade leading edges, especially in the case of RNG k-ε model.