Research Papers

Large-Eddy Simulation for Turbulent Heat Transfer

[+] Author and Article Information
Danesh K. Tafti

Mechanical Engineering Department,
Virginia Polytechnic Institute and State University,
114-I Randolph Hall, mail code 0238,
Blacksburg, VA 24061
e-mail: dtafti@vt.edu

Reference cited in Fig. 2 are [66].

Manuscript received September 18, 2012; final manuscript received February 20, 2013; published online May 17, 2013. Assoc. Editor: Srinath V. Ekkad.

J. Thermal Sci. Eng. Appl 5(2), 021001 (May 17, 2013) (13 pages) Paper No: TSEA-12-1156; doi: 10.1115/1.4023955 History: Received September 18, 2012; Revised February 20, 2013

The paper gives an overview of different components of conducting large-eddy simulations (LES) for convective heat transfer in practical applications. Subgrid stress models, wall models, and the generation of inlet turbulent boundary conditions are highlighted. For application to complex high Reynolds number flows, a two-layer LES wall model is used together with a synthetic eddy method (SEM) for generating turbulent inlet conditions for developing flows. Representative results highlighting LES predictions are given in a dimpled fin arrangement relevant to compact heat exchangers, in a simulated leading edge film cooling geometry, and in a developing ribbed duct and 180 deg turn relevant to turbine blade cooling. The use of LES wall modeling with the SEM is shown in an experimental can combustor with swirl, and finally a simulation which combines Reynolds-averaged Navier–Stokes (RANS) with wall modeled LES and SEM to predict combustor linear heat transfer is highlighted. It is shown that the combined use of these techniques can reduce computational time by at least an order of magnitude for developing flows. In all cases, predictions of mean turbulent quantities and heat transfer coefficients compare favorably with experiments.

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Fig. 8

Comparisons of heat transfer augmentation between the LES calculation and the mass transfer experiments of Han et al. [74] along the inner line, center line, and outer line of (a) the region upstream of the bend and (b) the region downstream of the bend show the good agreement between the calculations and experiments (Nu0 = 0.023Re0.8Pr0.4)

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Fig. 9

Swirl flow experimental setup of Wang et al. [76]

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Fig. 10

Measured and SEM predicted mean velocity and turbulent stress profiles at inlet of the computational domain (x*/H*= −2.1) (Re = 20,000, S = 0.43)

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Fig. 1

Dimple-protrusion fin geometry. Shaded area shows minimum computational unit.

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Fig. 2

Calculated friction coefficient Cf and Nusselt number Nuavg. Laminar baseline values use the theoretical laminar values in channel flow. In the turbulent regime the Petukhov and Gnielinski correlations for plane channel flow are used for friction as well as for Nusselt number [66].

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Fig. 3

Computational domain for simulated leading edge film cooling experiments

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Fig. 6

Comparison of LDV measurements with LES predictions in the center plane of the duct of the (a) streamwise velocity, (b) streamwise rms fluctuations, and (c) cross-stream rms fluctuations

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Fig. 7

Comparisons between the heat transfer LES calculations, experiments of Rau et al. [72], and IR measurements on (a) the centerline of the ribbed wall and (b) a vertical line on the smooth side wall upstream of the rib (Nu0 = 0.023Re0.8Pr0.4)

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Fig. 12

Schematic of experimental setup of Patil et al. [78]. From left to right: swirler, nozzle extension channel, can combustor. RANS domain is shown in red. WMLES domain is shown in blue and the interface between RANS and WMLES is shown by green line (D* = 203 mm, H* = 0.3D*) (swirl nozzle: Ri* = 0.11D*, Ro* = R1* = 0.2D*).

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Fig. 4

(a) Comparison of spanwise-averaged adiabatic effectiveness at B.R. = 0.4 with experimental data for different coolant pipe inlet conditions. (b) Spanwise-averaged adiabatic effectiveness at different blowing ratios. (c) Spanwise-averaged Frossling number or heat transfer coefficients at different blowing ratios. A distance of one jet diameter on the cylinder surface corresponds to approximately 7.2 deg. Thus at 70 deg, x*/d* ≈ 7.

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Fig. 5

Geometry of developing ribbed duct flow and 180 deg bend

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Fig. 11

Grid sensitivity study: (a) Time averaged mean swirl velocity at streamwise location x*/H*= 2.1 in radial plane. (b) Time averaged profiles of (from left to right) axial velocity (〈ux〉/Ub), swirl velocity (〈uθ〉/Ub), variance of axial velocity (〈ux'ux'¯〉/Ub2), variance of swirl velocity (〈uθ'uθ'¯〉/Ub2), and Reynolds shear stress at x*/H* = 2.1. Solid line: LES; dashed line: WMLES (Reynolds stresses are scaled up by a factor of 10).

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Fig. 13

(a) Contours of time mean axial velocity (ux/Ub) in azimuthal plane (z = 0). (b) Heat transfer augmentation ratio (Nu/Nu0) along the liner wall comparing IR experiments with LES (Nu0 = 0.023Re0.8Pr0.4).




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