Experimental and Analytical Study of the Effects of Free-Stream Turbulence on Turbulent Boundary Layers with Heat Transfer
Experimental and Analytical Study of the Effects of Free-Stream Turbulence on Turbulent Boundary Layers with Heat Transfer

Author: M. F. Blair

Publisher:

Published: 1982

Total Pages: 16

ISBN-13:

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Under the present investigation, detailed boundary layer turbulence structural data and turbulent heat transfer data were obtained for experimental test conditions and profile locations selected from the earlier text matrix. Numerous measurements assured that the present test conditions (boundary layer development and free-stream turbulence distributions) duplicated those of the earlier AFOSR contract. The purposes for making these present detailed boundary layer turbulence measurements were: (1) to provide data to which current finite-difference boundary layer turbulence models could be compared, and (2) to generate a data base for the development of new analytical models for boundary layer heat transfer prediction. The results from the present program have shown that the distributions of both the turbulence kinetic energy and the turbulence structural coefficients were affected by increased levels of free-stream turbulence. Local profile measurements indicated that the effect of increased free-stream turbulence was to decrease the near-wall turbulent Prandtl number relative to values expected for low free-stream turbulence. Turbulent Prandtl numbers in the outer region of the boundary layer were slightly increased for higher free-stream turbulence. A turbulence dependent correlation for the measured distribution of turbulent Prandtl number is given.

An Experimental and Analytical Study of Boundary Layers in Highly Turbulent Free-streams
An Experimental and Analytical Study of Boundary Layers in Highly Turbulent Free-streams

Author: M. F. Blair

Publisher:

Published: 1981

Total Pages: 21

ISBN-13:

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Research was conducted to examine two aspects of boundary layer flow: 1) the influence of free-stream turbulence on zero pressure gradient, full turbulent boundary layer flow; and 2) the combined effects of free-stream turbulence and favorable streamwise pressure gradients on transitional boundary layer flow. Keywords: Convective heat transfer coefficients; Boundary layer transition; Gas turbine airfoils; Boundary layer mean velocity; Experimental data. (edc).

An Experimental and Analytical Study of Boundary Layers in Highly Turbulent Freestreams
An Experimental and Analytical Study of Boundary Layers in Highly Turbulent Freestreams

Author: M. F. Blair

Publisher:

Published: 1979

Total Pages: 73

ISBN-13:

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Experimental research has been conducted to determine the influence of free-stream turbulence on zero pressure gradient, incompressible, fully turbulent boundary layer flow. During this period convective heat transfer coefficients, boundary layer mean velocity and temperature profile and wall static pressure distribution data were obtained for two flow conditions of constant free-stream velocity and low free-stream turbulence intensity and for one flow condition of constant free-stream velocity and higher free-stream turbulence. Documentation of the free-stream turbulence for these flows is currently in progress. The conclusion reached from the low free-stream turbulence test results is that these data are in excellent agreement with classic two-dimensional, low free-stream turbulence, turbulent boundary layer correlations, thus establishing the absolute accuracy of the experiment. The data obtained for the higher free-stream turbulence test case indicates that free-stream turbulence does have a significant effect on fully turbulent boundary layer skin friction and heat transfer. A quantitative assessment of this influence will emerge as data is obtained for additional free-stream turbulence levels and as the turbulence distributions are documented.

The Effects of Free-Stream Turbulence on the Turbulence Structure and Heat Transfer in Zero Pressure Gradient Boundary Layers
The Effects of Free-Stream Turbulence on the Turbulence Structure and Heat Transfer in Zero Pressure Gradient Boundary Layers

Author: M. F. Blair

Publisher:

Published: 1982

Total Pages: 193

ISBN-13:

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In an earlier funded investigation, experimental research was conducted to deterine the influence of free-stream turbulence on turbulent boundary layer heat transfer and mean profile development. The data obtained under this earlier contract indicated that both the skin friction and the heat transfer increased significantly with increased free-stream turbulence level. Under the present investigation, detailed boundary layer turbulence structural data and turbulent heat transfer data were obtained for experimental test conditions and profile locations selected from the earlier test matrix. Numerious measurements assured that the present test conditions (boundary layer development and free-stream turbulence distributions) duplicated those of the earlier contract. The purposes for making these present detailed boundary layer turbulence measurements were: to provide data to which current finite-difference boundary layer turbulence models could be compared, and to generate a data base for the development of new analytical models for bondary layer heat transfer prediction. With the completion of the experimental portion of this investigation, a theoretical effort was made to assess the capability of a finite difference boundary layer computer program, ABLE (Analysis of the Boundary Layer Equations) for predicting the effect of free-stream turbulence on momentum and thermal boundary layers.

Free-Stream Turbulence and Concave Curvature Effects on Heated, Transitional Boundary Layers
Free-Stream Turbulence and Concave Curvature Effects on Heated, Transitional Boundary Layers

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-24

Total Pages: 286

ISBN-13: 9781724222503

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An experimental investigation of the transition process on flat-plate and concave curved-wall boundary layers for various free-stream turbulence levels was performed. Results show that for transition of a flat-plate, the two forms of boundary layer behavior, identified as laminar-like and turbulent-like, cannot be thought of as separate Blasius and fully-turbulent profiles, respectively. Thus, simple transition models in which the desired quantity is assumed to be an average, weighted on intermittency, of the theoretical laminar and fully turbulent values is not expected to be successful. Deviation of the flow identified as laminar-like from theoretical laminar behavior is shown to be due to recovery after the passage of a turbulent spot, while deviation of the flow identified as turbulent-like from the full-turbulent values is thought to be due to incomplete establishment of the fully-turbulent power spectral distribution. Turbulent Prandtl numbers for the transitional flow, computed from measured shear stress, turbulent heat flux and mean velocity and temperature profiles, were less than unity. For the curved-wall case with low free-stream turbulence intensity, the existence of Gortler vortices on the concave wall within both laminar and turbulent flows was established using liquid crystal visualization and spanwise velocity and temperature traverses. Transition was found to occur via a vortex breakdown mode. The vortex wavelength was quite irregular in both the laminar and turbulent flows, but the vortices were stable in time and space. The upwash was found to be more unstable, with higher levels of u' and u'v', and lower skin friction coefficients and shape factors. Turbulent Prandtl numbers, measured using a triple-wire probe, were found to be near unity for all post-transitional profiles, indicating no gross violation of Reynolds analogy. No evidence of streamwise vortices was seen in the high turbulence intensity case. Kim, J. and Simon, T. W. Unspecified Cen...