Numerical Investigation of Wake Interaction in a Low Pressure Turbine

A time-accurate Reynolds-averaged Navier-Stokes solver has been extended for a phenomenological study of wake/bladerow interaction in a low pressure turbine near midspan. To qualitatively account for unsteady laminar-turbulent boundary layer transition, a variant of the Abu-Ghanam Shaw transition correlation has been coupled with the Spalart-Allmaras one-equation turbulence model. The method is shown to be capable of capturing separated-flow and wake-induced transition, as well as becalming and relaminarization effects. The model turbine investigated consists of three stator and two rotor rows. Instantaneous Mach number and eddy-viscosity plots are presented to monitor the wake migration and interaction with downstream boundary layers. Especially on the suction sides, very large fluctuations of the skin friction coefficient are observed. Effects of the near and far wakes are identified.