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Research Papers

Direct Numerical Simulation of Stagnation Point Heat Transfer Affected by Varying Wake-Induced Turbulence

[+] Author and Article Information
Lars Venema

e-mail: lars.venema@kit.edu

Hans-Jörg Bauer

Institut für Thermische
Strömungsmaschinen (ITS),
Karlsruhe Institute of Technology (KIT),
Karlsruhe 76131, Germany

Wolfgang Rodi

Institut für Hydromechanik (IfH),
Karlsruhe Institute of Technology (KIT),
Karlsruhe, 76131, Germany;
King Abdulaziz University,
Jeddah, Saudi Arabia

1Corresponding author.

2Current address: GE Global Research, Aerodynamics and Acoustics Lab, 85748 Garching/Munich, Germany.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received December 18, 2012; final manuscript received February 1, 2013; published online September 26, 2013. Editor: David Wisler.

J. Turbomach 136(2), 021008 (Sep 26, 2013) (7 pages) Paper No: TURBO-12-1246; doi: 10.1115/1.4023907 History: Received December 18, 2012; Revised February 01, 2013

In the present study the flow and heat transfer in a tandem cylinder setup are simulated by means of embedded direct numerical simulation (DNS). The influence of wake turbulence on the heat transfer in the stagnation region of the rear cylinder is investigated. The oncoming flow is varied by increasing the distance between the two cylinders, causing a change of the turbulent wake characteristics and the heat transfer. The data of both simulations show good agreement with an existing experimental correlation in the literature. For the small wake generator distance, a clear shift of the maximum heat transfer away from the stagnation line is observed. This shift is less pronounced for the larger distance.

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Figures

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Fig. 1

Schematic overview of the computational setup with the two wake generator distances

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Fig. 2

Block boundaries for l/D = 2. Each block has 40 × 40 cells in the XY plane. Indicated are the DNS zone (x/D < 0) and the LES zone (x/D > 0). The contour gives an impression of the temperature field in the wake of the heated cylinder.

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Fig. 3

Wake profiles of the mean velocity u between the wake generator and the heated cylinder stagnation point. The coordinates of the wake generator (x/D = −3.0) coincide.

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Fig. 4

Wake profiles of the mean velocity u between the wake generator and the heated cylinder stagnation point. The coordinates of stagnation points of the large cylinder (x/D = 0.0) coincide.

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Fig. 5

Flow characteristics along the centerline for both wake generator distances l/D. Displayed are the time-averaged streamwise velocity ⟨u⟩/U∞ and the turbulence intensity Tu; the coordinates of the wake generator coincide.

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Fig. 6

Flow characteristics along the centerline for both wake generator distances l/D. Displayed are the time-averaged streamwise velocity ⟨u⟩/U∞ and the turbulence intensity Tu; the coordinates of the stagnation points of the large cylinder coincide.

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Fig. 7

Instantaneous temperature field adjacent to cylinder surface at r/D = 0.502 for l/D = 2 (top left) and l/D = 3 (top right). Bottom figure shows instantaneous temperature field and velocity vectors in the plane normal to the cylinder surface at the stagnation line (θ = 0) for l/D = 3.

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Fig. 8

Comparison of the numerical simulations with the solution of [1] and experiments of [3], θ = 0 represents the stagnation point

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Fig. 9

Comparison of numerical simulations with the correlation of [2]. The symbols represent numerical simulations from the literature (open symbols) and the present study (filled symbols).

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