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Research Papers

Large Eddy Simulation on the Interactions of Wake and Film-Cooling Near a Leading Edge

[+] Author and Article Information
S. Sarkar

Professor
Mem. ASME
Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, UP 208016, India
e-mail: subra@iitk.ac.in

Harish Babu

Department of Mechanical Engineering,
Indian Institute of Technology Kanpur,
Kanpur, UP 208016, India
e-mail: harishb@iitk.ac.in

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 11, 2014; final manuscript received July 15, 2014; published online September 4, 2014. Editor: Ronald Bunker.

J. Turbomach 137(1), 011005 (Sep 04, 2014) (11 pages) Paper No: TURBO-14-1133; doi: 10.1115/1.4028219 History: Received July 11, 2014; Revised July 15, 2014

The unsteady flow physics due to interactions between a separated shear layer and film cooling jet apart from excitation of periodic passing wake are studied using large eddy simulation (LES). An aerofoil of constant thickness with rounded leading edge induced flow separation, while film cooling jets were injected normal to the crossflow a short distance downstream of the blend point. Wake data extracted from precursor LES of flow past a cylinder are used to replicate a moving bar that generates wakes in front of a cascade (in this case, an infinite row of the model aerofoils). This setup is a simplified representation of rotor-stator interaction in a film cooled gas turbine. The results of numerical simulation are presented to elucidate the formation, convection and breakdown of flow structures associated with the highly anisotropic flow involved in film cooling perturbed by convective wakes. The various vortical structures namely, horseshoe vortex, roller vortex, upright wake vortex, counter rotating vortex pair (CRVP), and downward spiral separation node (DSSN) vortex associated with film cooling are resolved. The effects of wake on the evolution of these structures are then discussed.

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References

Figures

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Fig. 1

A schematic of the wake-generating cylinders sweeping at a speed Vcyl ahead of the flat plate cascade (not to scale)

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Fig. 2

Details of film cooling holes

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Fig. 3

Grid resolution test for film cooling with uniform inlet considering mean streamwise velocity Um at different streamwise locations (refer Fig. 4 for legend)

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Fig. 4

Grid resolution test for film cooling with uniform inlet considering variation of mean film cooling effectiveness in the streamwise direction for different grid levels

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Fig. 5

(a) Mean streamwise velocity Um, (b) rms streamwise velocity fluctuation u′, left to right x/l = 0.22, 0.44, 0.66, 1.09, 1.27, 1.64, 2.55, ———, present computation; ○, experimental results [41]

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Fig. 6

Time averaged (a) centerline and (b) span-averaged effectiveness at different x/d locations, ———, present computation; ○, experimental results [42]

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Fig. 7

Vortical structures in JICF [17]

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Fig. 8

Instantaneous contours of streamwise velocity for flow with uniform inlet

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Fig. 9

Instantaneous contours of ωz indicating far field and near hole details for flow with uniform inlet

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Fig. 10

Instantaneous contours of ωy at y/d = 0.1 from wall for flow with uniform inlet

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Fig. 11

Instantaneous contours of streamwise vorticity ωx at different streamwise locations for flow with uniform inlet

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Fig. 12

Instantaneous contours of ωz along with streamlines for flow with uniform inlet

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Fig. 13

Instantaneous contours of ωy for flow with uniform inlet

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Fig. 14

Instantaneous isosurface of −λ2 corresponding to 0.25 along with in plane velocity vector for plane x/d = 3, z/d = 1.5, and y/d = 0.25 from top to bottom for flow with uniform inlet

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Fig. 15

Instantaneous contours of ωz at t/tp = 0.50

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Fig. 16

Instantaneous contours of ωz at t/tp = 0.55

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Fig. 17

Instantaneous contours of ωy at t/tp = 0.50 in xz plane

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Fig. 18

Instantaneous contours of ωy at t/tp = 0.55 in xz plane

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Fig. 19

Instantaneous contours of ωx at t/tp = 0.50 at different streamwise locations

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Fig. 20

Instantaneous contours of ωx at t/tp = 0.55 at different streamwise locations

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Fig. 21

Instantaneous contours of T* at t/tp = 0.50

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Fig. 22

Instantaneous contours of T* at t/tp = 0.55

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Fig. 23

Instantaneous contours of T* (flood) along with that of ωx (lines) at t/tp = 0.50 at different yz planes

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Fig. 24

Instantaneous contours of T* (flood) along with that of ωx (lines) at t/tp = 0.55 at different streamwise locations

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Fig. 25

Contours of η superimposed with −λ2 at t/tp = 0.5

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Fig. 26

Contours of η superimposed with −λ2 at t/tp = 0.55

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Fig. 27

Instantaneous contours of T* at t/tp = 0.15 in xy (top) and xz (bottom) planes

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Fig. 28

Instantaneous contours of T* for flow with uniform inlet in xy (top) and xz (bottom) planes

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Fig. 29

Contours of η superimposed with isosurface of −λ2 at t/tp = 0.15

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Fig. 30

Contours of η superimposed with isosurface of −λ2 for flow with uniform inlet

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