Implicit Large Eddy Simulation of a Stalled Low Pressure Turbine Airfoil

Abstract

Timeaccurate numerical simulations were conducted on the aftloaded L1A lowpressure turbine airfoil at a Reynolds number of 22,000 (based on inlet velocity magnitude and axial chord length). This flow condition produces a nonreattaching laminar separation zone on the airfoil suction surface. The numerical code TURBO is used to simulate this flow field as an implicit large eddy simulation (ILES). Generally, good agreement was found when compared to experimental timeaveraged and instantaneous flow measurements. The numerical separation zone is slightly larger than that in the experiments, though integrated wake loss values improved from Reynoldsaveraged Navier–Stokes (RANS)based simulations. Instantaneous snapshots of the numerical flow field showed the Kelvin Helmholtz instability forming in the separated shear layer and a largescale vortex shedding pattern at the airfoil trailing edge. These features were observed in the experiments with similar sizes and vorticity levels. Power spectral density analyses revealed a global passage oscillation in the numerics that was not observed experimentally. This oscillation was most likely a primary resonant frequency of the numerical domain.