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Research Papers: Forced Convection

Numerical Simulations of the Near-Field Region of Film Cooling Jets Under High Free Stream Turbulence: Application of RANS and Hybrid URANS/Large Eddy Simulation Models

[+] Author and Article Information
Hosein Foroutan

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: hosein@psu.edu

Savas Yavuzkurt

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: sqy@psu.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received March 3, 2014; final manuscript received September 18, 2014; published online November 5, 2014. Assoc. Editor: Danesh K. Tafti.

J. Heat Transfer 137(1), 011701 (Jan 01, 2015) (12 pages) Paper No: HT-14-1109; doi: 10.1115/1.4028646 History: Received March 03, 2014; Revised September 18, 2014

This paper investigates the flow field and thermal characteristics in the near-field region of film cooling jets through numerical simulations using Reynolds-averaged Navier–Stokes (RANS) and hybrid unsteady RANS (URANS)/large eddy simulation (LES) models. Detailed simulations of flow and thermal fields of a single-row of film cooling cylindrical holes with 30 deg inline injection on a flat plate are obtained for low (M = 0.5) and high (M = 1.5) blowing ratios under high free stream turbulence (FST) (10%). The realizable k‐ε model is used within the RANS framework and a realizable k‐ε-based detached eddy simulation (DES) is used as a hybrid URANS/LES model. Both models are used together with the two-layer zonal model for near-wall simulations. Steady and time-averaged unsteady film cooling effectiveness obtained using these models are compared with available experimental data. It is shown that hybrid URANS/LES models (DES in the present paper) predict more mixing both in the wall-normal and spanwise directions compared to RANS models, while unsteady asymmetric vortical structures of the flow can also be captured. The turbulent heat flux components predicted by the DES model are higher than those obtained by the RANS simulations, resulting in enhanced turbulent heat transfer between the jet and mainstream, and consequently better predictions of the effectiveness. Nevertheless, there still exist some discrepancies between numerical results and experimental data. Furthermore, the unsteady physics of jet and crossflow interactions and the jet lift-off under high FST is studied using the present DES results.

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Figures

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Fig. 4

Wall-normal distributions of the turbulence intensity just upstream of the cooling hole (x/D = −2)

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Fig. 3

Close-up of the midplane view of the grid near the injection region

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Fig. 2

Schematic lateral and top view of the computational domain

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Fig. 1

Schematic view of the test setup in experimental study of Mayhew et al. [37], also showing the computational domain in this study

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Fig. 5

Contours of (a) steady, (b) time-averaged, and (c) instantaneous dimensionless temperature at the mid-plane for M = 0.5. Steady results are obtained using RANS and time-averaged and instantaneous results are obtained using DES simulations.

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Fig. 17

Distributions of the nondimensional spanwise turbulent heat flux at three streamwise locations for M = 1.5, comparison of the RANS (- - - -) and the DES () simulations

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Fig. 12

(a) Steady, (b) time-averaged, and (c) instantaneous dimensionless temperature at a spanwise plane (x/D = 1) for M = 1.5

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Fig. 13

Spanwise distributions of the film cooling effectiveness at three streamwise locations (x/D = 0.1, 1, and 5) obtained using the DES () and the RANS (- - - -) turbulence closure approaches (M = 1.5)

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Fig. 14

Details of the vortical structures in the film cooling flow for M = 1.5, (a) side view and (b) top view

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Fig. 15

Distributions of the nondimensional streamwise turbulent heat flux at three streamwise locations for M = 1.5, comparison of the RANS (- - - -) and the DES () simulations

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Fig. 16

Distributions of the nondimensional wall-normal turbulent heat flux at three streamwise locations for M = 1.5, comparison of the RANS (- - - -) and the DES () simulations

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Fig. 18

Film cooling centerline effectiveness for M = 1.5, comparison of RANS and DES

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Fig. 19

Film cooling spanwise-averaged effectiveness for M = 1.5, comparison of RANS and DES

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Fig. 6

(a) Steady, (b) time-averaged, and (c) instantaneous dimensionless temperature at a spanwise plane (x/D = 1) for M = 0.5

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Fig. 7

Spanwise distributions of the film cooling effectiveness at three streamwise locations (x/D = 0.1, 1, and 5) obtained using the DES () and the RANS (- - - -) turbulence closure approaches (M = 0.5)

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Fig. 8

Contours of film cooling effectiveness, (a) experimental data [37], (b) steady RANS results, and (c) time-averaged DES results, M = 0.5

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Fig. 9

Film cooling centerline effectiveness for M = 0.5, comparison of RANS and DES

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Fig. 10

Film cooling spanwise-averaged effectiveness for M = 0.5, comparison of RANS and DES

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Fig. 11

Contours of (a) steady, (b) time-averaged, and (c) instantaneous dimensionless temperature at the midplane for M = 1.5. Steady results are obtained using RANS and time-averaged and instantaneous results are obtained using DES simulations.

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Fig. 20

Distributions of LES and RANS regions in DES computations for (a) M = 0.5 and (b) M = 1.5 together with instantaneous dimensionless temperature contours at a spanwise plane (x/D = 5)

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