Similarity-Law Entrainment Method for Thick Axisymmetric Turbulent Boundary Layers in Pressure Gradients


Book Description

Analytical relations have been derived for calculating developing thick, axisymmetric, turbulent boundary layer in a pressure gradient from two simultaneous differential equations: momentum and shape parameter. An entrainment method is used to obtain the shape parameter equation. Both equations incorporate the velocity similarity laws that provide a two-parameter velocity profile general enough to include any range of Reynolds numbers. Newly defined quadratic shape parameters which arise from the geometry of the thick axisymmetric boundary layer are analytically related to the two-dimensional shape parameter by means of these velocity similarity laws. The variation of momentum loss, boundary-layer thickness, local skin friction, and local velocity profile may be calculated for the axisymmetric turbulent boundary layers on underwater bodies, including the thick boundary layers on the tails. The various formulations are shown to correlate well with available experimental data. (Author).




Similarity-law Entrainment Method for Thick Axisymmetric Turbulent Boundary Layers in Pressure Gradients


Book Description

Analytical relations have been derived for calculating developing thick, axisymmetric, turbulent boundary layer in a pressure gradient from two simultaneous differential equations: momentum and shape parameter. An entrainment method is used to obtain the shape parameter equation. Both equations incorporate the velocity similarity laws that provide a two-parameter velocity profile general enough to include any range of Reynolds numbers. Newly defined quadratic shape parameters which arise from the geometry of the thick axisymmetric boundary layer are analytically related to the two-dimensional shape parameter by means of these velocity similarity laws. The variation of momentum loss, boundary-layer thickness, local skin friction, and local velocity profile may be calculated for the axisymmetric turbulent boundary layers on underwater bodies, including the thick boundary layers on the tails. The various formulations are shown to correlate well with available experimental data. (Author).




Similarity-law Entrainment Method for Two-dimensional Turbulent Boundary Layers in Pressure Gradients


Book Description

Analytical relations have been derived for calculating a developing two-dimensional turbulent boundary layer in a pressure gradient from two simultaneous differential equations: momentum and shape parameter. An entrainment method is used to obtained the shape parameter equation. Both equations incorporate the velocity similarity laws that provide a two-parameter velocity profile general enough to include any range of Reynolds numbers. The entrainment factor is based on the characteristics of equilibrium pressure gradients in a way which can accommodate the usual pressure gradients found in engineering applications. The method includes a newly formed wake modification for the similarity laws as well as added effects due to low Reynolds numbers. The variation of momentum loss boundary-layer thickness, local skin friction, and local velocity profile may be calculated for the boundary layers on hydrofoils and two-dimensional appendages. The various formulations are shown to correlate well with available experimental data. (Author).







Turbulent Shear Flows I


Book Description

The present book contains papers that have been selected from contributions to the First International Symposium on Turbulent Shear Flows which was held from the 18th to 20th April 1977 at The Pennsylvania State University, University Park, Pennsylvania, USA. Attend ees from close to 20 countries presented over 100 contributions at this meeting in which many aspects of the current activities in turbulence research were covered. Five topics received particular attention at the Symposium: Free Flows Wall Flows Recirculating Flows Developments in Reynolds Stress Closures New Directions in Modeling This is also reflected in the five chapters of this book with contributions from research workers from different countries. Each chapter covers the most valuable contributions of the conference to the particular chapter topic. Of course, there were many additional good con tributions to each subject at the meeting but the limitation imposed on the length of this volume required that a selection be made. The realization of the First International Symposium on Turbulent Shear Flows was p- sible by the general support of: U. S. Army Research Office U. S. Navy Research Office Continuing Education Center of The Pennsylvania State University The conference organization was carried out by the organizing committee consisting of: F. Durst, Universitat Karlsruhe, Karlsruhe, Fed. Rep. of Germany V. W. Goldschmidt, Purdue University, West Lafayette, Ind. , USA B. E. Launder, University of California, Davis, Calif. , USA F. W. Schmidt, Pennsylvania State University, University Park, Penna.




Thick Axisymmetric Turbulent Boundary Layer and Near Wake of a Low-drag Body of Revolution


Book Description

Detailed measurements of pressure distributions, mean velocity profiles and Reynolds stresses were made in the thick, axisymmetric boundary layer and the near wake of a low-drag body of revolution. The data are presented in graphical as well as tabular form for convenience in later analysis. These measurements shed some light on the joint influence of transverse and longitudinal surface curvatures and pressure gradients on the boundary-layer development and on the manner in which an axisymmetric boundary layer becomes a fully-developed wake. Apart from giving a complete set of data on such an important flow configuration, the measurements should provide a fairly rigorous test case for some of the recent turbulence closure models which claim a level of generality not achieved by the older phenomenological models. By inclusion of recently proposed modifications to account for the effects of the extra rates of strain on the turbulence length scale arising from longitudinal and transverse surface curvatures, it is shown that the boundary layer in the tail region of a body of revolution is dominated by the extra strain rates and that more research is needed to account for them properly even in the most recent calculation procedures.




An Analytical Solution of the Thick Axisymmetric Turbulent Boundary Layer on a Long Cylinder of Constant Radius


Book Description

Two similarity laws for a thick, axisymmetric, turbulent boundary layer on a long circular cylinder have been established. The validity of the assumption of constant-stress moment in the law-of-the-wall region is analyzed under the assumption of similarity. A new logarithmic mixing length, which takes into consideration the effect of transverse curvature on turbulence, is proposed for the law-of-the-wall region. With this logarithmic mixing-length models, the mean-flow momentum equation yields a law-of-the-wall relation in terms of the exponential integral in the logarithmic portion of the inner layer. Comparisons with available data and other proposed relations reveal that this logarithmic law gives a definite improvement. Also a mathematical explanation is given as to why the cylinder data do not deviate appreciably from the classical two-dimensional law-of-the-wall, even though it is observed that the turbulent characteristics, such as the size of large eddies and the turbulent intensities are much smaller than for a flat plate.




Analysis of Turbulent Boundary Layers


Book Description

Analysis of Turbulent Boundary Layers focuses on turbulent flows meeting the requirements for the boundary-layer or thin-shear-layer approximations. Its approach is devising relatively fundamental, and often subtle, empirical engineering correlations, which are then introduced into various forms of describing equations for final solution. After introducing the topic on turbulence, the book examines the conservation equations for compressible turbulent flows, boundary-layer equations, and general behavior of turbulent boundary layers. The latter chapters describe the CS method for calculating two-dimensional and axisymmetric laminar and turbulent boundary layers. This book will be useful to readers who have advanced knowledge in fluid mechanics, especially to engineers who study the important problems of design.