The Effects of Free-Stream Turbulence on the Turbulence Structure and Heat Transfer in Zero Pressure Gradient Boundary Layers PDF Download
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Author: M. F. Blair Publisher: ISBN: Category : Languages : en Pages : 193
Book Description
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.
Author: M. F. Blair Publisher: ISBN: Category : Languages : en Pages : 193
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Experimental research has been conducted to determine the influence of free-stream turbulence on zero pressure gradient fully turbulent boundary layer flow. During this period convective heat transfer coefficients, boundary layer mean velocity and temperature profile data, and wall static pressure distribution data were obtained for five flow conditions of constant free-stream velocity and free-stream turbulence intensities ranging from approximately 1/4% to 7%. Free-stream multi-component turbulence intensity, longitudinal integral scale, and spectral distributions were obtained for the various turbulence levels. The test results with 1/4% free-stream turbulence indicate 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 test cases with higher free-stream turbulence indicate that the turbulence has a significant effect on turbulent boundary layer skin friction and heat transfer. It has been shown that these effects are a function of the free-stream turbulence intensity, the turbulence length scale, and the boundary layer momentum thickness Reynolds number. Suggested correlations for the influence of free-stream turbulence on skin friction, heat transfer, and Reynolds analogy factor are given. Also during this period, a boundary layer prediction method has been assessed as to its ability to predict free-stream turbulence effects on flat plate heating and skin friction. Comparisons with the experimental data obtained here showed that adequate predictions can be made for this case with an existing turbulence model. (Author).
Author: P. Bradshaw Publisher: Springer Science & Business Media ISBN: 3662225689 Category : Science Languages : en Pages : 345
Book Description
Turbulent transport of momentum, heat and matter dominates many of the fluid flows found in physics, engineering and the environmental sciences. Complicated unsteady motions which mayor may not count as turbulence are found in interstellar dust clouds and in the larger blood vessels. The fascination of this nonlinear, irreversible stochastic process for pure scientists is demonstrated by the contributions made to its understanding by several of the most distinguished mathematical physicists of this century, and its importance to engineers is evident from the wide variety of industries which have contributed to, or benefit from, our current knowledge. Several books on turbulence have appeared in recent years. Taken collectively, they illustrate the depth of the subject, from basic principles accessible to undergraduates to elaborate mathematical solutions representing many years of work, but there is no one account which emphasizes its breadth. For this, a multi-author work is necessary. This book is an introduction to our state of knowledge of turbulence in most of the branches of science which have contributed to that knowledge. It is not a Markovian sequence of unrelated essays, and we have not simply assembled specialized accounts of turbulence problems in each branch; this book is a unified treatment, with the material classified according to phenomena rather than application, and freed as far as possible from discipline-oriented detail. The approach is "applied" rather than "pure" with the aim of helping people who need to under stand or predict turbulence in real life.
Author: J. D. A. Walker Publisher: ISBN: Category : Fluid dynamics Languages : en Pages : 47
Book Description
"The prediction of the influence of freestream turbulence on boundary layer properties such as wall heat transfer, skin friction and the integral thicknesses is investigated using the model of McDonald, Fish and Kreskovsky; the model is critically discussed in detail. In addition, an assessment is made both of the overall performance of the model and of the numerical finite difference procedures used to implement the model in a current UTRC prediction code. Detailed comparisons are made with recently obtained experimental data, taken over a wide range of freestream turbulence and pressure gradient conditions. In an overall sense, the turbulence model provided good predictions for the skin friction and integral boundary layer properties in fully developed zero pressure gradient flows; relatively good qualitative levels of the solutions were encountered. For favorable pressure gradient flows, the behavior in the transition zone was only captured qualitatively. Generally, it is concluded that the model provides a reasonable basis for further development to accurately account for mainstream turbulence effects in boundary layers; however, in view of difficulties encountered in using the code, a need to revise the numerical procedures is indicated."--Abstract.
Author: Michael F. Blair Publisher: ISBN: Category : Languages : en Pages : 219
Book Description
A combined experimental and analytical program has been conducted to examine transitional, accelerating boundary layer flows with high levels of freestream turbulence. An earlier program focused on measurement of transitional heat transfer distributions for four combinations of streamwise acceleration and freestream turbulence. The present program was designed to document the boundary layer turbulence structure and spectral distributions for the same four test conditions. The results from the present program have shown that transition in accelerating flows consists of an acceleration dominated stage of slowly developing intermittency followed by a second stage with the same general characteristics as zero-pressure-gradient transition. Conditionally sampled fluctuating velocity profile measurements indicated that the boundary layer turbulence was highly anisotropic in the early stages of transition. Conditionally sampled mean velocity measurements showed that within the intermittent turbulent patches the mean velocity profiles were very similar to those of an equilibrium turbulent boundary layer. Spectral distribution data indicated that preferred amplification of the most unstable (as predicted by linear stability theory) frequencies occurred upstream of the onset of transitional bursting. In addition to the experimental portion of this investigation, numerical experiments were undertaken to assess the ability of currently existing methods to predict heat transfer during transition in accelerating flows.
Author: Peter W. Runstadler Publisher: ISBN: Category : Boundary layer Languages : en Pages : 326
Book Description
A combination of visual and quantitative measurements is presented, providing a physical picture of the turbulent boundary layer flow structure on a flat plate. The flow structure is shown to consist of three zones, each zone has a one to one correspondence to the well known regions of the u+, y+ mean velocity profile. A wall layer region is shown to exist below y+ = 10. An apparently fully turbulent region exists corresponding to the logarithmic ''law of the wall'' and the ''buffer'' region. An intermittent zone appears to agree closely with the ''wake'' deviation region. An entirely new result of the investigation is the delineation of the structure of the wall layer region. This region is shown to contain a relatively regular structure of low and high velocity fluid streaks alternating in the span direction, together with the ejection of low momentum fluid into the outer flow. Correlations are given for the rate of ejection and the streak spacing. A qualitative description of other features of the wall layer region and the character of the remainder of the boundary layer flow structure is presented. (Author).
Author: M. F. Blair Publisher: ISBN: Category : Languages : en Pages : 73
Book Description
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.
Author: M. F. Blair
Author: M. F. Blair
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Author: P. Bradshaw
Author: Robert P. Dring
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Author: J. D. A. Walker
Author: Michael F. Blair
Author: Peter W. Runstadler
Author: M. F. Blair
Author: Virgil A. Sandborn