Closure to “Discussion of ‘An Experimental Investigation of Incompressible Channel Flow Near Transition’” (1977, ASME J. Fluids Eng., 99, p. 698)

1977 ◽  
Vol 99 (4) ◽  
pp. 698-698
Author(s):  
N. A. Feliss ◽  
M. C. Potter ◽  
M. C. Smith
2007 ◽  
Vol 28 (5) ◽  
pp. 435-443 ◽  
Author(s):  
Fantu A. Tereda ◽  
N. Srihari ◽  
Bengt Sunden ◽  
Sarit K. Das

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Carlos Silva ◽  
Doseo Park ◽  
Egidio (Ed) Marotta ◽  
Leroy (Skip) Fletcher

The effect of the dimple shape and orientation on the heat transfer coefficient of a vertical fin surface was determined both numerically and experimentally. The investigation focused on the laminar channel flow between fins, with a Re=500 and 1000. Numerical simulations were performed using a commercial computational fluid dynamics code to analyze optimum configurations, and then an experimental investigation was conducted on flat and dimpled surfaces for comparison purposes. Numerical results indicated that oval dimples with their “long” axis oriented perpendicular to the direction of the flow offered the best thermal improvement, hence the overall Nusselt number increased up to 10.6% for the dimpled surface. Experimental work confirmed these results with a wall-averaged temperature reduction of up to 3.7K, which depended on the heat load and the Reynolds number. Pressure losses due to the dimple patterning were also briefly explored numerically in this work.


Author(s):  
Wenwu Zhou ◽  
Hui Hu ◽  
Yu Rao

Due to the dimple’s unique characteristics of comparatively low pressure loss penalty and good heat transfer enhancement performance, dimple provides a very desirable alternative internal cooling technique for gas turbine blades. In the present study, an experimental investigation was conducted to quantify the flow characteristics over staggered dimple arrays and to examine the vortex structures inside the dimples. In addition to the surface pressure measurements, a high-resolution digital Particle Image Velocimetry (PIV) system was also utilized to achieve detailed flow field measurements to quantify the characteristics of the turbulent channel flow over the dimple arrays in terms of the ensemble-averaged velocity, Reynolds shear stress and turbulence kinetic energy (TKE) distributions. The experimental measurement results show that the friction factor of the dimpled surface is much higher than that of a flat surface. The measured pressure distribution within a dimple reveals clearly that flow separation and attachment would occur inside each dimple. In comparison with those of a conventional channel flow with flat surface, the channel flow over the dimpled arrays was found to have much stronger Reynolds stress and higher TKE level. Such unique flow characteristics are believed to be the reasons why a dimpled surface would have a better heat transfer enhancement performance for internal cooling of turbine blades as reported in those previous studies.


Author(s):  
Hélio Augusto Goulart Diniz ◽  
Lúcio Sant'Anna Purri Miranda ◽  
Ivo Zatti Lima Meyer ◽  
Luiz Henrique Ramos de Oliveira ◽  
Jorge Luis Zegarra Tarqui

1945 ◽  
Vol 12 (2) ◽  
pp. A91-A100
Author(s):  
E. R. Van Driest

Abstract Turbulence diffusion in open-channel flow was investigated experimentally by photographing the spread of globules formed by the injection of an immiscible fluid into water. The mean-square transverse deviations of the globules at various distances downstream from the source were computed and analyzed in an effort to determine the shape of the velocity-correlation curve. Comparison was made between two types of curve which fitted the deviation data, one corresponding to a power-correlation law and the other to an exponential-correlation law.


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