Download or read book Examining the Effects of a Controled Turbulent Velocity Field on a Passive Scalar written by Don O'Regan and published by . This book was released on 2005 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Length Scales on the Mixing of Passive Scalars in Grid Turbulence written by Abdullah MohammadFarid N. Alkudsi and published by . This book was released on 2012 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of passive scalars in turbulence research is a technologically important topic. This study seeks to investigate the effect of the variation of integral length scale, and scalar injector size and separation on turbulent mixing. The study is motivated by devices such as the simple gas turbine pre-mixer where these three relevant length scales are present. Heated wakes of different sizes and separations are produced by heating various sets of thin wires in a horizontal wire grid. The horizontal wire screen is placed downstream of biplane grids of different mesh sizes. Time-resolved velocity and temperature are measured by a dual hot and cold wire probe. Assessments of the effect of the array of thin wires used as the scalar generator on the velocity and scalar fields behind the turbulence grid are presented. The evolution of the profiles of the first four statistical moments of temperature fluctuations across the wake with downstream distance is studied for various scalar injector size and separation for several integral length scales. Specifically, the downstream evolution of a single thermal wake is studied for source sizes that range from less than the Kolmogorov to larger than the integral length scale. Also included in the study the downstream evolution and interaction of two thermal wakes is also presented. For the single wake, the wake growth, sufficiently far from the generator, for all source sizes is found to be consistent with the assumption that the effective diffusivity is constant across the wake. The evolution of the effective diffusivity with downstream distance is found to be independent of the source size and identical to the evolution of the effective diffusivity of a line source in the same velocity field. The effects of changing the velocity integral scale are governed by the effect of the integral scale on the evolution of the effective turbulent diffusivity. Those effects are found to be similar in character to the effect on a line source. The mean scalar of two sources is found to be the sum of the mean of the individual sources. Higher statistical moments show more complex relationships.
Download or read book Effect of Background Turbulence on the Scalar Field of a Turbulent Jet written by Alejandro Perez Alvarado and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The effect of background turbulence on the scalar field of an axisymmetric turbulent jet is investigated experimentally. The present investigation builds on the work of Gaskin et al. (2004), who studied the concentration and velocity fields of a plane jet in a shallow coflow with different turbulence levels and Khorsandi et al. (2013), who studied the velocity field of an axisymmetric turbulent jet emitted into a turbulent background. Different driving algorithms for a large RJA were tested and the statistics of the turbulence generated downstream of the RJA were compared to characterize the algorithms' performance. Variations in the spatial configuration of jets operating at any given instant, as well as in the statistics of their on/off times were studied. The algorithm identified as RANDOM generated the closest approximation of zero-mean-flow homogeneous isotropic turbulence. The flow generated by the RANDOM algorithm had a relatively high turbulent Reynolds number (ReT = uTl/[nu] = 2360, where uT is a characteristic RMS velocity, l is the integral length scale of the flow, [nu] is the kinematic viscosity of the water) and the integral length scale (l = 11.6 cm) is the largest reported to date. Thus, RANDOM algorithm was used to generate the background turbulence for the investigation of scalar mixing within a turbulent jet.The effect of background turbulence on the mixing of a passive scalar within a turbulent jet at different Reynolds numbers was investigated. To this end, planar laser-induced fluorescence was employed to obtain concentration measurements of dye (disodium fluorescein, Schmidt number = 2000) within the jet. Two jet Reynolds numbers (Re=UjD/[nu], where Uj is the jet exit velocity, D is the nozzle diameter and [nu] is the kinematic viscosity of the jet fluid, water) were studied: 10600 and 5800. The resulting statistics of the scalar fields showed that the mean concentrations of jets emitted into turbulent backgrounds were lower than those of jets emitted into a quiescent background near the centerline. However, near the edges of the jet (r/x>0.15), the concentrations were higher for the jets issued into turbulent surroundings. The RMS concentrations of the jet emitted into a turbulent background significantly increased. Examination of the probability density functions of concentration revealed a higher degree of intermittency of the scalar field. The probability of low concentrations increased in the presence of background turbulence although the maximum concentrations were comparable to those of the jet emitted into a quiescent background. Flow visualizations revealed meandering of the jet issued into background turbulence, which is associated with the increased probability of lower concentrations and higher intermittency. Additionally, the widths of the jets emitted into a turbulent background were increased. For the lower jet Reynolds number, the described effects were more evident and the jet structure was destroyed by the background turbulence within the measurement region, resulting in flat radial profiles of both the mean and RMS concentrations. Comparison of the results of the scalar field with those of the hydrodynamic jet of Khorsandi et al. (2013) revealed a similar behavior of the two fields. However, the most significant difference was the larger radial extent of the profiles of mean and RMS concentrations, which resulted from the meandering of the jet and increased transport of scalar by turbulent diffusion. The flow visualizations suggest that the entrainment and mixing in the jet in a turbulent background changes with the destruction of jet structure, from jet driven entrainment to become potentially dominated by i) increased lateral advection of the jet by large scales of the background turbulence during the meandering of the jet, which is subsequently mixed by its smaller scales, and ii) turbulent diffusion that is significantly enhanced by the turbulent background." --
Download or read book The Distortion of Turbulent Velocity and Passive Scalar Fields written by Hamid Reza Rahai and published by . This book was released on 1988 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Impingement Jet Cooling in Gas Turbines written by R.S. Amano and published by WIT Press. This book was released on 2014-05-28 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the requirement for enhanced cooling technologies on modern gas turbine engines, advanced research and development has had to take place in field of thermal engineering. Among the gas turbine cooling technologies, impingement jet cooling is one of the most effective in terms of cooling effectiveness, manufacturability and cost. The chapters contained in this book describe research on state-of-the-art and advanced cooling technologies that have been developed, or that are being researched, with a variety of approaches from theoretical, experimental, and CFD studies. The authors of the chapters have been selected from some of the most active researchers and scientists on the subject. This is the first to book published on the topics of gas turbines and heat transfer to focus on impingement cooling alone.
Download or read book Theoretical Investigation of a Passive Scalar Such as Temperature in Isotropic Turbulence written by Robert McDougall Kerr and published by . This book was released on 1981 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mixing of a Passive Scalar in Isotropic and Sheared Homogeneous Turbulence written by E. Shirani and published by . This book was released on 1981 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to calculate the velocity and passive scalar fields in homogeneous turbulent flows, the three-dimensional, time-dependent equations of motion and the diffusion equation have been solved numerically.
Download or read book Japanese Science and Technology 1983 1984 written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch and published by . This book was released on 1985 with total page 1080 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Index to Theses with Abstracts Accepted for Higher Degrees by the Universities of Great Britain and Ireland and the Council for National Academic Awards written by and published by . This book was released on 2006 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Air Sea Interaction written by F. Dobson and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 797 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the past decade, man's centuries-old interest in marine me teorology and oceanography has broadened. Ocean and atmosphere are now treated as coupled parts of one system; the resulting interest in air-sea interaction problems has led to a rapid growth in the sophistication of instruments and measurement techniques. This book has been designed as a reference text which describes, albng with the instruments themselves, the accumulated practical experi ence of experts engaged in field observations of air-sea interac tions. It is meant to supplement rather than replace manuals on standard routine observations or instnunentation handbooks. At the inception a textbook was planned, which would contain only well tested methods and instruments. It was quickly discovered that for the book to be useful many devices and techniques would have to be included which are still evolving rapidly. The reader is therefore cautioned to take nothing in these pages for granted. Certainly, every contributor is an expert, but while some are back ed up by generations of published work, others are pioneers. The choice of topics, of course, is debatable. The types of observa tions included are not exhaustive and topics such as marine aero sols and radio-tracers are omitted, as was the general subject of remote sensing, which was felt to be too broad and evol ving too rapidly. The guideline adopted in limiting size was maximum use fulness to 'a trained experimentalist new to the field'.
Download or read book Studying Turbulence Using Numerical Simulation Databases written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications written by United States. Superintendent of Documents and published by . This book was released on 1991 with total page 1434 pages. Available in PDF, EPUB and Kindle. Book excerpt: February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Small scale Structure of Passive Scalar Mixing in Turbulent Boundary Layers written by Lakshmi P. Dasi and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective is to contribute to several issues regarding the traditional view of the local structure of passive scalar fields: (1) probability density function (PDF) of the scalar concentration and scalar gradient, (2) the scalar power spectrum, (3) the structure functions, and (4) correlation functions and multi-point correlators. In addition, the research provides a geometric description of two-dimensional transects of the passive scalar iso-surfaces using the tools of fractal geometry. The local structure is analyzed as a function of large-scale anisotropy, intermittency factor, Reynolds number, and initial condition of the scalar injection. Experiments were performed in the bed boundary layer produced by a uniform depth open channel flow of water in a tilting flume for Re [subscript lambda] = 63, 94, and 120. A small nozzle iso-kinetically delivers a passive scalar of high Schmidt number (Sc = 1000) at mid-depth to generate the turbulent scalar field. Three nozzle diameters are used to study the effects of the injection length scale. High-resolution planar laser induced fluorescence (PLIF) technique is used to measure the scalar field. The local structure far from isotropic and is influenced even at the smallest scales by large-scale anisotropy, initial injection length scale and the Reynolds number of the flow. The PDF of the scalar fluctuations is non-Gaussian and dependent on large-scale anisotropy. The PDF of scalar gradients show the influence of large-scale anisotropy on the structure at the smallest scales. The spectrum of the scalar field deviates from the k [superscript -5/3] prediction in the inertial convection regime and is dependent on large-scale anisotropy, external intermittency, and low Reynolds number. There is no evidence of Batchelors k [superscript -1] scaling law. The scaling exponents of the even-ordered structure functions appear to be inversely correlated with the kurtosis of the scalar fluctuations. The fractal geometry of the two dimensional transects of passive scalar iso-surfaces is scale dependent. The fractal dimension is 1.0 at the smallest length scale and increases in a universal manner in the viscous-convective regime. The coverage length underestimate reflects this universal behavior with practical significance. The lacunarity function shows that the instantaneous scalar field is most in-homogenous around the Kolmogorov scale.
Download or read book Simultaneous Measurements of Velocity and Temperature in the Heated Wake of a Cylinder with Applications to the Modeling of Turbulent Passive Scalars written by Arpi Berajeklian and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
