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Research Papers

# Influence of Wake Structure on Unsteady Flow in a Low Pressure Turbine Blade Passage

[+] Author and Article Information
S. Sarkar

Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, Indiasubra@iitk.ac.in

J. Turbomach 131(4), 041016 (Jul 09, 2009) (14 pages) doi:10.1115/1.3072490 History: Received August 27, 2008; Revised September 14, 2008; Published July 09, 2009

## Abstract

The effect of wake structures on the evolution of the boundary layer over the suction side of a high-lift low-pressure turbine blade is studied using large-eddy simulation (LES) for a Reynolds number $Re=7.8×104$ (based on the axial chord and the inlet velocity). The wake data of different characteristics (defined by the wake deficit and the small-scale motion) are extracted from a precursor LES of flow past a cylinder. This replaces a moving bar that generates wakes in front of a cascade. LES results illustrate that apart from the wake kinematics, the large pressure oscillations and rollup of the separated shear layer along the rear half of the suction surface depend on the length scale of the convective wake. The transition of this rolled-up shear layer is influenced by the wake turbulence and the small-scale motion.

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## Figures

Figure 1

Geometry of T106 low-pressure cascade and a schematic of a row of wake-generating cylinders sweeping at a speed Ub ahead of the cascade

Figure 2

Contours of time-averaged (a) pressure coefficient (dashed lines indicate negative values), (b) streamwise Reynolds normal stress u′2¯, (c) cross-flow Reynolds normal stress v′2¯, and (d) Reynolds shear stress u′v′¯

Figure 3

Instantaneous vorticity depicting wake structure: (a) 3D simulation and (b) 2D simulation (presented in different scales)

Figure 4

Contours of time-averaged TKE near the cylinder: (a) 3D simulation and (b) 2D simulation

Figure 5

Instantaneous isosurface of vorticity |ω| at four equal time intervals through the wake passing cycle for the simulation 3DW

Figure 6

Instantaneous isosurface of vorticity |ω| at four equal time intervals through the wake passing cycle for the simulation 2DW

Figure 7

Phase-averaged perturbation of velocity vectors at two time intervals through the wake passing cycle: simulations (a) 3DW and (b) 2DW

Figure 8

Phase-averaged contours of nondimensional turbulent kinetic energy: (a) simulation 3DW, (b) experiment by Stieger and Hodson (23), and (c) simulation 2DW

Figure 9

Phase-averaged contours of production: simulations (a) 3DW and (b) 2DW

Figure 10

Time-averaged Cp distributions on the T106 blade: present LES and experiment by Stieger (11)

Figure 11

Time-averaged velocity profiles and their derivatives at three sections along the suction surface: the firm line represents the simulation 3DW, and the dashed line represents the simulation 2DW

Figure 12

Phase-averaged ⟨Cp⟩ distributions on the rear half of the suction surface: present LES and experiment by Stieger (11), simulations (a) 3DW and (b) 2DW

Figure 13

Phase-averaged spanwise vorticity on the rear half of the suction surface: simulations (a) 3DW and (b) 2DW (the location of the wake centerline is marked by a circle)

Figure 14

Streamwise component of phase-averaged velocity perturbations ⟨u⟩-u¯ along a section of boundary layer on the suction surface

Figure 15

Velocity fluctuations (rms and phase averaged) at two sections of boundary layer along the rear half of the suction surface: simulations (a) 3DW and (b) 2DW

Figure 16

Instantaneous isosurface of spanwise component of vorticity illustrating the formation of 3D vortex loops on the rear half of the suction surface: simulations (a) 3DW and (b) 2DW

Figure 17

Phase-averaged contours of nondimensional TKE on the rear half of the suction surface during the interaction of wake and separated boundary layer: simulations (a) 3DW and (b) 2DW (the location of the wake centerline is marked by a circle)

Figure 18

Phase-averaged contours of nondimensional production on the rear half of the suction surface during the interaction of wake and separated boundary layer: simulations (a) 3DW and (b) 2DW

Figure 19

Time-averaged profiles of TKE and production on the rear half of the suction surface: simulations (a) 3DW and (b) 2DW

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