Download or read book Characterization of Flow in Coaxial Jet Mixers written by Stuart Owen Holiday and published by . This book was released on 1996 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure Mixing and Dynamics of Controlled Single and Coaxial Jets in Crossflow written by Elijah Weston Harris and published by . This book was released on 2020 with total page 493 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes an experimental study of the instability, structural, dynamical, and mixing characteristics of jets in crossflow (JICF). Constituent species of the jet fluid were nitrogen and helium, with additional seeding of tracer particulates for implementation in non-intrusive laser diagnostics of acetone planar laser induced fluorescence (PLIF) imaging, and particle image velocimetry (PIV). Various jet-to-crossflow momentum flux ratios in the range of $61\leq J\leq5$ were investigated for three alternative flush mounted circular contracting nozzle injector configurations: a small nozzle ($D=4.04~mm$) passively augmented by a small triangular tab placed about the jet exit periphery, a large nozzle ($D=7.59~mm$) actively augmented by axisymmetric excitation of the jet flow, and a coaxial nozzle ($D=3.81~mm$) with varying degrees of counterflow applied in the outer annulus. Hotwire anemometry was implemented for investigations of the instabilities along the upstream and downstream shear layers of the jet flow, in addition to more in depth analysis of the dynamics of the flow from application of time series analysis techniques to the signal. PLIF imaging served to characterize the JICF by providing qualitative visualizations of the flowfield, and quantitative measurements of the scalar field concentrations and mixing metrics, along both the centerplane and cross-sectional planes of the developing jet. PIV provided determination of the velocity and vorticity fields, along with further investigation of the flow dynamics from proper orthogonal decomposition (POD) analysis, again from both the centerplane and cross-sectional planes of the developing jet. Flow conditions corresponding to a naturally absolutely unstable (AU) upstream shear layer (USL) ($J = 7$) and a convectively unstable (CU) condition ($J = 61$) with jet Reynolds numbers of $Re_j=2300$ were explored for PLIF imaging of the tabbed JICF. Tab location was seen in some cases to significantly alter shear layer instabilities, especially for the case with $J = 7$. Yet acetone planar laser induced fluorescence (PLIF) imaging revealed that more substantive structural changes could be realized with tab placement for the case where $J = 61$. Tab locations with the greatest influence appeared to be consistent with wavemaker regions predicted in numerical simulations of the round transverse jet by \cite{Regan}, providing evidence for the potential to tailor local shear layer rollup, jet structure, and mixing via simple passive geometrical alterations. For the PIV imaging different $J$ values were explored, ranging from naturally AU USL, for $J = 5$ and 8, to naturally CU conditions, for $J = 20$ and 41, with $Re_j=1900$. Placement of the tab at or near the upstream region of the jet exit caused a delay in shear layer rollup and, as quantified from the PIV, a reduction in USL vorticity associated with a thickening of the upstream jet momentum thickness. Tab placement was observed to have a symmetrizing influence on nearfield cross-sectional vorticity dynamics at high and low $J$ values, though specific tab locations had differing degrees of influence for different flow conditions. Proper orthogonal decomposition (POD) modes extracted from centerplane velocity field measurements showed significant influence of tab placement on jet upstream as well as wake structures, depending on $J$. Phase portraits extracted from POD mode coefficient plots produced periodic (circular) shapes for tab placement corresponding to conditions for which the USL was determined to be absolutely unstable. Flow conditions corresponding to a naturally AU USL ($J = 7$) and a CU condition ($J = 10$) with $Re_j=1800$ were explored for PLIF imaging of the axisymmetrically excited JICF. Implementation of a novel double-pulse waveform demonstrated significant enhancement of the quantified jet mixing, where the most significant alterations was seen for forcing waveforms which generated nearfield vortical interactions and breakdown. The same forcing waveform yielded differences between the AU and CU jets resulting from changes to the formation number of the vortex rings as suggested by \cite{Sau_10}, which resulted in alterations in the celerity, circulation, and nearfield interaction of said vortex rings. Separate investigations treated a jet with a stronger AU USL ($J=6$) to comparing the novel double-pulse forcing with sinusoidal and square wave excitation of the jet. Synchronization analysis demonstrated dramatic improvement in the ability of the jet to lock-in to the forcing when a square or double-pulse waveform was implemented. Additional Van der Pol oscillator modeling of Fourier approximated square wave forcing suggested greater significance was seen in the proximity of the harmonics to the natural instability of the jet compared to the actual coherence of the waveform, analogoous to findings by \cite{Sau_10}. Interestingly, PIV-based POD further suggested the nearfield dynamics and efficacy of mixing were heavily dependent upon the vortex rings which were formed, in some cases quite independent of the state of synchronization to the applied forcing. Application of a quasiperiodic forcing significantly improved the mixing without significantly altering the jet structure. For the coaxial JICF, a single flow condition corresponding to a CU USL with a naturally highly asymmetric cross-section ($J = 41$), at $Re_j=1900$, was explored with PLIF and PIV imaging. Suction was applied locally in the upstream and downstream edges of the jet in order to alter the jet shear layer instabilities and vortex dynamics. Indeed, hotwire based spectral characteristics along the USL demonstrated the jet transitioned to an AU flow with strong suction upstream. PIV-based POD also depicted significant enhancement of mode structures along the USL of the jet. Hotwire spectral measurements detected little alteration to the USL with suction applied in the downstream of the jet, where the jet remained CU even with strong suction. However, PIV-based POD dynamics depicted significant enhancement of structures downstream which resembled upright wake vortices, and appeared coupled with the vortex rollup along the downstream of the jet. Interestingly, the corresponding cross-sectional CVP structure was made quite symmetric with the suction applied both upstream or downstream of the jet, suggestive that the suction applied along the symmetry plane of the jet was able to overcome the jet's natural susceptibility to asymmetric perturbations (\cite{Alves_2}), and further supported the suggested wavemaker region for a CU jet purported by \cite{Regan}. Mixing metrics determined significant enhancement in mixing due to the applied suction, further establishing agreement in the correlation between the strength of the shear layer dynamics, symmetry of the cross-sectional CVP, and the resulting jet mixing.

Download or read book Analysis of Mixing of Coaxial Streams of Dissimilar Fluids Including Energy generation Terms written by Herbert Weinstein and published by . This book was released on 1964 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Mixing in Nonreactive and Reactive Flows written by S. Murthy and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 469 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulence, mixing and the mutual interaction of turbulence and chemistry continue to remain perplexing and impregnable in the fron tiers of fluid mechanics. The past ten years have brought enormous advances in computers and computational techniques on the one hand and in measurements and data processing on the other. The impact of such capabilities has led to a revolution both in the understanding of the structure of turbulence as well as in the predictive methods for application in technology. The early ideas on turbulence being an array of complicated phenomena and having some form of reasonably strong coherent struc ture have become well substantiated in recent experimental work. We are still at the very beginning of understanding all of the aspects of such coherence and of the possibilities of incorporating such structure into the analytical models for even those cases where the thin shear layer approximation may be valid. Nevertheless a distinguished body of "eddy chasers" has come into existence. The structure of mixing layers which has been studied for some years in terms of correlations and spectral analysis is also getting better understood. Both probability concepts such as intermittency and conditional sampling as well as the concept of large scale structure and the associated strain seem to indicate possibilities of distinguishing and synthesizing 'engulfment' and molecular mixing.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Engineering Turbulence Modelling and Experiments 2 written by F. Martelli and published by Elsevier. This book was released on 2014-06-28 with total page 1012 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today understanding turbulence is one of the key issues in tackling flow problems in engineering. Powerful computers and numerical methods are now available for solving flow equations, but the simulation of turbulence effects, which are nearly always important in practice, are still at an early stage of development. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulence momentum, heat and mass transfer. The 89 papers, including 5 invited papers, in this volume present and discuss new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. The high standard of the contributions on the developing and testing of turbulent models attests to the world-wide interest this domain is currently attracting from researchers.

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1968 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Scientific and Technical Reports written by United States. National Aeronautics and Space Administration Scientific and Technical Information Division and published by . This book was released on with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Selected Listing of NASA Scientific and Technical Reports written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Division and published by . This book was released on 1969 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Technical Abstract Bulletin written by and published by . This book was released on with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cumulated Index Medicus written by and published by . This book was released on 1996 with total page 1354 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microfluidic Devices in Nanotechnology written by Challa S. S. R. Kumar and published by John Wiley & Sons. This book was released on 2010-11-29 with total page 561 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explores the latest applications arising from the intersection of nanotechnology and microfluidics In the past two decades, microfluidics research has seen phenomenal growth, with many new and emerging applications in fields ranging from chemistry, physics, and biology to engineering. With the emergence of nanotechnology, microfluidics is currently undergoing dramatic changes, embracing the rising field of nanofluidics. This volume reviews the latest devices and applications stemming from the merging of nanotechnology with microfludics in such areas as drug discovery, bio-sensing, catalysis, electrophoresis, enzymatic reactions, and nanomaterial synthesis. Each of the ten chapters is written by a leading pioneer at the intersection of nanotechnology and microfluidics. Readers not only learn about new applications, but also discover which futuristic devices and applications are likely to be developed. Topics explored in this volume include: New lab-on-a-chip systems for drug delivery Integration of microfluidics with nanoneuroscience to study the nervous system at the single-cell level Recent applications of nanoparticles within microfluidic channels for electrochemical and optical affinity biosensing Novel microfluidic approaches for the synthesis of nanomaterials Next-generation alternative energy portable power devices References in each chapter guide readers to the primary literature for further investigation of individual topics. Overall, scientists, researchers, engineers, and students will not only gain a new perspective on what has been done, but also the nanotechnology tools they need to develop the next generation of microfluidic devices and applications. Microfluidic Devices for Nanotechnology is a two-volume publication, the first ever to explore the synergies between microfluidics and nanotechnology. The first volume covers fundamental concepts; this second volume examines applications.

Download or read book Unified Analysis of Turbulent Jet Mixing written by Joseph A. Schetz and published by . This book was released on 1969 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents a unified model for the eddy viscosity in jet mixing flows. The successful boundary layer model due to Clauser is given a new interpretation that permits generalization to a wide variety of turbulent flows.

Download or read book U S Government Research Reports written by and published by . This book was released on 1964 with total page 870 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coaxial jet Mixing in a Liquid Flow system written by Donald W. Simonds and published by . This book was released on 1952 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Mixing in the Initial Region of Heterogeneous Axisymmetric Coaxial Confined Jets written by Kirti N. Ghia and published by . This book was released on 1970 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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: