Influence of High Mainstream Turbulence on Leading Edge Heat Transfer

Mehendale, A. B.; Han, Je-Chin; Ou, Shichuan

doi:10.1115/1.2911212

Cited by 57 publications

(21 citation statements)

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“…Upon applying the Hiemenz transformation, the combination of -^ emerges as a parameter that controls the shape of the turbulent mean velocity and thermal profiles. This parameter later forms the basis of many empirical correlations, including Smith and Kuethe (1966); Kestin and Wood (1971); Lowery and Vachon (1975); Mehendale et al (1991). These correlations fit the Frossling number Fr = J^ (Frossling, 1940) all using a second order polynomial of T^ but with slightly diffierent coefficients by different investigators.…”

Section: Experimental Studiesmentioning

confidence: 99%

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Zhang¹,

Lele²

2004

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Public reporting burden for this collection of information is estinuted to awrage 1 hour per response, including the time for reviewing in maintaining the data needed, and completing and reviewing tWs ooHedion of infbrmatian. SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTKppi'oved fcv PMV.1 1 c rclsnsa, distribution unlikiiLoLl SUPPLEMENTARY NOTES 03914. ABSTRACT Stagnation point flow and heat transfer in the presence of free-stream turbulence is investigated through both numerical simulation and theoretical analysis. Large eddy simulations (LES) results for different free-stream turbulent intensity, length scale, and Mach number are reported. The Reynolds stress statistics and budgets are obtained and presented. The numerical results show good agreement with experimental measurements on elevated heat transfer coefficient, and reveals the characteristic vortical flow structures responsible for the observed heat transfer enhancement.The theoretical analysis shows that the vorticity amplification, and hence the heat transfer enhancement, increases with decreasing length scale and reaches a maximum value at about five times the boundary layer thickness. A new correlation for heat transfer enhancement which incorporates turbulence intensity, integral length scale and mean flow Reynolds number is derived and shown to reasonably collapse the recent experimental data. Abstract Stagnation point flow and heat transfer in the presence of free-stream turbulence is investigated through both numerical simulation and theoretical analysis. Large eddy simulations (LES), using fourth order finite difference in curvilinear coordinates and an efficient dual time linearized sub-iteration scheme, are performed to investigate free-stream turbulence impingement upon an elliptical leading edge and the resulting heat transfer enhancement. A new blending procedure is developed through which independent, statistically identical realizations of homogeneous isotropic turbulence are combined to provide realistic representations of free-stream turbulence.Results for diflTerent free-stream turbulent intensity, length scale, and Mach number are reported. Strong anisotropy of the turbulence due to the mean flow strain is observed as the stagnation point is approached. The Reynolds stress statistics and budgets are obtained and presented. These results are expected to provide unique data for turbulence modelling of strain dominated flows. The numerical results show good agreement with the experimental measurements on elevated heat transfer coefficient. It also reveals that small scale, intense vortical flow structures generated at the leading edge by vortex stretching induces significant changes in local thermal boundary layer, causing the observed heat transfer enhancement.In the theoretical study, the distortion of three dimensional unsteady disturbance in an incompressible Hiemenz boundary layer and its effect on the wall heat transfer is analyzed based on linear vortex dynamics. An asymptotic solution for disturbanc...

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Section: Experimental Studiesmentioning

confidence: 99%

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Zhang¹,

Lele²

2004

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“…The correlations were only a function of the turbulence intensity (Tu) and cylinder Reynolds number (Re), length scale was not included in these studies as it was in later work on cylinders and in most of the work on flat plates. Mehendale, et al (1991) later modified the correlation for a larger range of turbulence levels up to 15%.…”

Section: Cylinder Experimentsmentioning

confidence: 99%

Effects of High Intensity, Large-Scale Freestream Combustor Turbulence on Heat Transfer in Transonic Turbine Blades

Nix¹,

Diller²,

Ng³

2003

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“…It has been known for many years that free stream turbulence can augment stagnation region heat transfer (Giedt, 1951Seban, 1960; however, results of experiments are inconsistent and attempts to correlate heat transfer augmentation as a function of turbulence intensity and Reynolds number while ignoring the length scale (Zapp, 1950;Schnautz, 1958;Smith and Kuethe, 1966;Kestin and Wood, 1971;Mehendale et Ames used three different diameter cylinders to investigate stagnation region heat transfer; his data were well correlated using his new parameter. The data of several other researchers (Lowery and Vachon, 1975;Dyban et al, 1975) A dual channel spectrum analyzer was used to obtain autocorrelation data.…”

Section: Introductionmentioning

confidence: 99%

Measurements of the Influence of Integral Length Scale on Stagnation Region Heat Transfer

Fossen

Ching

1996

International Journal of Rotating Machinery

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The purpose of the present work was twofold: first, to determine if a length scale existed that would cause the greatest augmentation in stagnation region heat transfer for a given turbulence intensity and second, to develop a prediction tool for stagnation heat transfer in the presence of free stream turbulence. Toward this end, a model with a circular leading edge was fabricated with heat transfer gages in the stagnation region. The model was qualified in a low turbulence wind tunnel by comparing measurements with Frossling's solution for stagnation region heat transfer in a laminar free stream. Five turbulence generating grids were fabricated; four were square mesh, biplane grids made from square bars. Each had identical mesh to bar width ratio but different bar widths. The fifth grid was an array of fine parallel wires that were perpendicular to the axis of the cylindrical leading edge. Turbulence intensity and integral length scale were measured as a function of distance from the grids. Stagnation region heat transfer was measured at various distances downstream of each grid.Data were taken at cylinder Reynolds numbers ranging from 42,000 to 193,000. Turbulence intensities were in the range 1.1 to 15.9 percent while the ratio of integral length scale to cylinder diameter ranged from 0.05 to 0.30. Stagnation region heat transfer augmentation increased with decreasing length scale. An optimum scale was not found. A correlation was developed that fit heat transfer data for the square bar grids to within +4%. The data from the array of wires were not predicted by the correlation; augmentation was higher for this case indicating that the degree of isotropy in the turbulent flow field has a large effect on stagnation heat transfer. The data of other researchers are also compared with the correlation.

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Influence of High Mainstream Turbulence on Leading Edge Heat Transfer

Cited by 57 publications

References 0 publications

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Effects of High Intensity, Large-Scale Freestream Combustor Turbulence on Heat Transfer in Transonic Turbine Blades

Measurements of the Influence of Integral Length Scale on Stagnation Region Heat Transfer

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