Download or read book Statistical Analyses of Fractal Grid Generated Turbulence written by Adrian Chin Hsiung Chong and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Multiple Scales on Fractal grid generated Turbulence written by Alexis Kathleen Omilion and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fractal grids, having patterns that repeat at different length scales, mimic the multi-scale characteristic of objects of complex appearance in nature, such as branching pulmonary network, river network, trees, and cumulus clouds. Understanding the role that multiple length scales have in momentum and energy transport is essential for effective utilization of fractal grids in a wide variety of engineering applications. While previous studies have solidified the dominant effect of the largest scale of fractal grids, effects of the additional scales on the generated turbulent flow remain unclear. This research is to determine how the smaller fractal scales (and the interaction between the multiple scales) influence the turbulence statistics of the induced flow and the pressure drop across a fractal square grid using well-controlled water-tunnel experiments. Instantaneous and ensemble-averaged velocity fields are obtained by a planar Particle Image Velocimetry (PIV) for a set of fractal square grids (N = 1, 2, 3 and 4) at the Reynolds number of 3400. The static pressure drop across the grids are measured by a differential pressure transducer. Flow fields indicate that the multiple jets, wakes and the shear layers produced by the multiple scales are the fundamental flow physics that promote momentum transport in the turbulence. In addition, the multiple scales cause a redistribution of the turbulent kinetic energy and a change in the vortex shedding mechanism behind the grids. The grid of 3 fractal scales (N = 3) produces higher turbulence intensity levels than the grid with 4 fractal scales (N = 4) despite having a lower blockage ratio and pressure drop, owing to the suppression of vortex shedding by the additional scale of the grid of N = 4. To better predict the location of peak turbulence intensity, the wake interaction length scale model is modified to incorporate the effects of the interactions among multiple scales by the effective mesh size and an empirical scaling coefficient Beta. Considering the capability of fractal grids to enhance momentum and energy transport, this work can potentially benefit a wide variety of applications where energy-efficient mixing or convective heat transfer is a key process.

Download or read book Analysis and Application of Decaying Turbulence with Initial Fractal Geometry written by Hiroki Suzuki and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, we address high-Schmidt-number (Sc) scalar turbulent mixing that results from grid-generated turbulence using the initial fractal geometry of the velocity profile. More specifically, as was proposed in our recent study, we adopt an initial flow field generated by a fractal grid and apply it to a water channel experiment based on a high-Sc-number scalar-mixing layer in order to create grid-generated turbulence, and thus solve our current research problem. The high-Sc-number scalar and velocity fields of the grid-generated turbulence are then measured using planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV), respectively. By means of fractal analysis, this study specifically addresses the turbulent mixing phenomena in which the fractal dimension of the mixing interface of an observed high-Sc-number scalar field is calculated. Additionally, we discuss the efficiency of using fractal grids as devices for enhancing high-Sc-number scalar turbulent mixing by observing turbulent intensities and dissipation by PIV.

Download or read book Experimental Study of Turbulence Generation and Control by Fractal Grids written by S. M. M. Salim and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence generation and control have been an immense interest among scientists and researchers due to the fact that nearly all industrial flows are turbulent. In some cases, turbulence is highly desired, for example chemical plants need higher turbulence for the efficient mixing of various substances whereas, in oil and pipe industries, whereas, turbulence in the pipe flows causes higher energy input to sustain the flow along the pipe length. Thus, control of turbulence directly contributes to cutting costs. The existing approaches to control such flows are case specific and no single universal approach exists owing to the lack of understanding of underlying physics. Many approaches have been taken to generate turbulence in laboratory set-ups for the past hundred years to study turbulence control. One such approach is the use of a rectangular grid through which the fluid is forced to generate so called grid turbulence. In contrast, we have made use of fractal geometry to generate turbulence for similar study. The self-similar edge characteristic of the fractal grids is thought to play the vital role in the enhanced mixing properties. Four sets of fractal grids, each with equal flow area, were used in the study. Our results from the experiments conducted in a circular wind tunnel indicate that it is possible to significantly improve the generation and control of turbulence by the introduced fractal approach.

Download or read book The Effects of Grid generated Turbulence on Flat and Concave Turbulent Boundary Layers written by Paul Leslie Johnson and published by . This book was released on 1989 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Statistical Theories and Computational Approaches to Turbulence written by Y. Kaneda and published by Springer. This book was released on 2002-10-14 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the papers presented at the workshop on Statistical The ories and Computational Approaches to Turbulence: Modern Perspectives and Applications to Global-Scale Flows, held October 10-13, 2001, at Nagoya Uni versity, Nagoya, Japan. Because of recent developments in computational capabilities, the compu tational approach is showing the potential to resolve a much wider range of length and time scales in turbulent physical systems. Nevertheless, even with the largest supercomputers of the foreseeable future, development of adequate modeling techniques for at least some scales of motion will be necessary for practical computations of important problems such as weather forecasting and the prediction and control of global pollution. The more powerful the available machines become, the more demand there will be for precise prediction of the systems. This means that more precise and reliable knowledge of the underlying dynamics will become important, and that more efficient and precise numerical methods best adapted to the new generation of computers will be necessary. The understanding of the nature of unresolved scales then will playa key role in the modeling of turbulent motion. The challenge to turbulence theory here is to elucidate the physics or dynamics of those scales, in particular their sta tistical aspects, and thereby develop models on sound bases to reduce modeling ambiguity. The challenge to the computational method is to develop efficient algorithms suitable for the problems, the machines, and the developed models.

Download or read book Statistical Analysis of Atmospheric Turbulence about a Simulated Block Building written by Sidney L. Steely and published by . This book was released on 1981 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fractal Classical and Active Grid Turbulence written by Robert Jason Hearst and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Windtunnel Turbulence Generated by Square Fractal Grids written by Richard Elian Seoud and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Statistical Properties and Similarity of Line Integrated Concentration Fluctuations Across Plumes Diffusing in Grid generated Turbulence written by M. Poreh and published by . This book was released on 1993 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Statistical Analysis of Turbulence Using a Large Scale Digital Computing System written by Robert Eugene Pierce and published by . This book was released on 1972 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Decay of Windtunnel Turbulence Generated from Square Fractal Grids written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of a Contraction on Grid generated Turbulence written by Yong Oun Han and published by . This book was released on 1988 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Grid Generated Turbulence with and Without Rotation about the Streamwise Direction written by Roald Arnold Wigeland and published by . This book was released on 1978 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Compressiblity Effects in Grid generated Turbulence written by G. Briassulis and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Wind tunnel Contraction on Grid generated Turbulence written by Chang-Shu Fu and published by . This book was released on 1981 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Progress in Turbulence III written by Joachim Peinke and published by Springer Science & Business Media. This book was released on 2009-12-28 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: This third issue on “progress in turbulence” is based on the third ITI conference (ITI interdisciplinary turbulence initiative), which took place in Bertinoro, North Italy. Researchers from the engineering and physical sciences gathered to present latest results on the rather notorious difficult and essentially unsolved problem of turbulence. This challenge is driving us in doing basic as well as applied research. Clear progress can be seen from these contributions in different aspects. New - phisticated methods achieve more and more insights into the underlying compl- ity of turbulence. The increasing power of computational methods allows studying flows in more details. Increasing demands of high precision large turbulence - periments become aware. In further applications turbulence seem to play a central issue. As such a new field this time the impact of turbulence on the wind energy conversion process has been chosen. Beside all progress our ability to numerically calculate high Reynolds number turbulent flows from Navier-Stokes equations at high precision, say the drag co- ficient of an airfoil below one percent, is rather limited, not to speak of our lack of knowledge to compute this analytically from first principles. This is rather - markable since the fundamental equations of fluid flow, the Navier-Stokes eq- tions, have been known for more than 150 years.