The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6 percent. Boundary layer measurements were conducted for two constant-K cases, K1 = −0.51 × 10−6 and K2 = −1.05 × 10−6. The fluctuation quantities, u′, ν′, t′, the Reynolds shear stress (uν), and the Reynolds heat fluxes (νt and ut) were measured. In general, u′/U∞, ν′/U∞, and νt have higher values across the boundary layer for the adverse pressure-gradient cases than they do for the baseline case (K = 0). The development of ν′ for the adverse pressure gradients was more actively involved than that of the baseline. In the early transition region, the Reynolds shear stress distribution for the K2 case showed a near-wall region of high-turbulent shear generated at Y+ = 7. At stations farther downstream, this near-wall shear reduced in magnitude, while a second region of high-turbulent shear developed at Y+ = 70. For the baseline case, however, the maximum turbulent shear in the transition region was generated at Y+ = 70, and no near-wall high-shear region was seen. Stronger adverse pressure gradients appear to produce more uniform and higher t′ in the near-wall region (Y+ < 20) in both transitional and turbulent boundary layers. The instantaneous velocity signals did not show any clear turbulent/nonturbulent demarcations in the transition region. Increasingly stronger adverse pressure gradients seemed to produce large non turbulent unsteadiness (or instability waves) at a similar magnitude as the turbulent fluctuations such that the production of turbulent spots was obscured. The turbulent spots could not be identified visually or through conventional conditional-sampling schemes. In addition, the streamwise evolution of eddy viscosity, turbulent thermal diffusivity, and Prt, are also presented.
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October 1996
Research Papers
The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 2—Fluctuation Quantities
S. P. Mislevy,
S. P. Mislevy
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634-0921
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T. Wang
T. Wang
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634-0921
Search for other works by this author on:
S. P. Mislevy
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634-0921
T. Wang
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634-0921
J. Turbomach. Oct 1996, 118(4): 728-736 (9 pages)
Published Online: October 1, 1996
Article history
Received:
February 4, 1995
Online:
January 29, 2008
Connected Content
This is a companion to:
Development of Air-Cooled Ceramic Nozzles for a Power-Generating Gas Turbine
Citation
Mislevy, S. P., and Wang, T. (October 1, 1996). "The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 2—Fluctuation Quantities." ASME. J. Turbomach. October 1996; 118(4): 728–736. https://doi.org/10.1115/1.2840928
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