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Research Papers

Numerical Simulation of a Turbulent Flow Over a Backward Facing Step With Heated Wall: Effect of Pulsating Velocity and Oscillating Wall

[+] Author and Article Information
A. K. Pozarlik

e-mail: a.k.pozarlik@utwente.nl

J. B. W. Kok

Laboratory of Thermal Engineering, University of Twente,
P.O. Box 217,
7500 AE Enschede,The Netherlands

1Corresponding author.

Manuscript received April 20, 2012; final manuscript received July 31, 2012; published online October 12, 2012. Assoc. Editor: Bengt Sunden.

J. Thermal Sci. Eng. Appl 4(4), 041005 (Oct 12, 2012) (9 pages) doi:10.1115/1.4007278 History: Received April 20, 2012; Revised July 31, 2012

An accurate prediction of the flow and the thermal boundary layer is required to properly simulate gas to wall heat transfer in a turbulent flow. This is studied with a view to application to gas turbine combustors. A typical gas turbine combustion chamber flow presents similarities with the well-studied case of turbulent flow over a backward facing step, especially in the near-wall regions where the heat transfer phenomena take place. However, the combustion flow in a gas turbine engine is often of a dynamic nature and enclosed by a vibrating liner. Therefore apart from steady state situations, cases with an oscillatory inlet flow and vibrating walls are investigated. Results of steady state and transient calculations for the flow field, friction coefficient, and heat transfer coefficient, with the use of various turbulence models, are compared with literature data. It has been observed that the variations in the excitation frequency of the inlet flow and wall vibrations have an influence on the instantaneous heat transfer coefficient profile. However, significant effect on the time mean value and position of the heat transfer peak is only visible for the inlet velocity profile fluctuations with frequency approximately equal to the turbulence bursting frequency.

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References

Figures

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Fig. 1

Geometry, coordinate system, and flow pattern for the backward facing step calculations

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Fig. 2

Velocity profiles at location x/H = 3, 4.47, 6.67, 8.87 for various 3D and 2D geometries

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Fig. 3

Comparison of the skin friction coefficient and the Stanton number for the k-ε, k-ω, and SST turbulence model

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Fig. 4

Temperature profiles at different locations (from top-left: x/Xr = 0.05; 0.25; 0.65; 1.05; 1.45; 2.25)

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Fig. 5

Velocity profiles at various locations (from top-left: x/Xr = 0.33; 0.56; 0.67; 0.89; 1.00; 1.33)

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Fig. 6

Turbulence intensity at various locations (from top-left: x/Xr = 0.33; 0.56; 0.67; 0.89; 1.00; 1.33)

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Fig. 7

Stream-function of the SST model for velocity pulsations with the excitation frequency of 10 Hz (Umean = 11.3 m/s): phase (from top-left) 2/5π (U = 13.1 m/s); 6/5π (U = 10.6 m/s); 8/5π (U = 9.0 m/s); 2π (U = 10.6 m/s), where 2π = 20th sample

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Fig. 8

Mean and transient results of the skin friction coefficient—10 Hz case with pulsating inlet velocity

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Fig. 9

Mean skin friction coefficient profiles for various excitation frequencies

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Fig. 10

Mean and transient results of the Stanton number—10 Hz case with pulsating inlet velocity

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Fig. 11

Mean Stanton number profiles for different excitation frequencies

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Fig. 12

Instantaneous and mean values of the skin friction coefficient for calculations with moving wall

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Fig. 13

Instantaneous and mean values of the Stanton number for calculations with moving wall

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