Title: Large-Eddy Simulation of wake convection and unsteady flow in an LP turbine blade passage

Authors: S. Sarkar

Addresses: Department of Mechanical Engineering, Indian Institute of Technology, Kanpur – 208016, India

Abstract: The Large-Eddy Simulations (LES) of unsteady flows within the passage of a highly cambered Low-Pressure (LP) turbine blade (T106 profile) interacted by impinging wakes are performed for a Reynolds number of 1.6 × 10⁵ (based on the chord and exit velocity). The wake-data generated from a precursor LES are interpolated at the inlet plane of the cascade replacing a moving bar wake-generator in front of it. The three-dimensional, time-dependent, incompressible Navier-Stokes equations in fully covariant form are solved using a symmetry-preserving finite difference scheme of second-order spatial and temporal accuracy. An attempt is made to describe the effects of wake kinematics and wake turbulence on the development of unsteady boundary layer on the suction surface of the LP turbine blade. When compared with experiments, the present LES qualitatively resolves high production of Turbulent Kinetic Energy (TKE) due to distortion of migrating wakes within the blade passage. Interactions of this turbulent wake with the inflexional boundary layer on the rear half of the suction surface trigger rollup of shear layer via Kelvin-Helmholtz (K–H) instabilities leading to transition. This results in increased level of turbulence along the last 20% of the suction surface length.

Keywords: blade-wake interactions; low pressure turbine blades; unsteady flow; LES; large eddy simulation; wake convection; impinging wakes; Navier-Stokes equations; wake kinematics; wake turbulence; suction surface; CFD; computational fluid dynamics.

DOI: 10.1504/PCFD.2007.014961

Progress in Computational Fluid Dynamics, An International Journal, 2007 Vol.7 No.7, pp.387 - 403

Published online: 28 Aug 2007 *

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