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Author:
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 193
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Book Description
A jet in cross flow (JICF) is examined experimentally by injecting a stream of air into crossing fluid with an aim into quantifying entrainment process and downstream evolution. The behavior of JICF is important to fields ranging from turbine-blade cooling to smokestack pollution and volcanic eruption dynamics. Existing simplified volcanic plume models are tested; most importantly, the near-field contributions of complex interconnected vortex systems, which present significant uncertainties because they assume negligible turbulence. While jets in irrotational cross-flow have been investigated, this analysis has focused on the interaction between a turbulent jet in low and highly turbulent cross-flow created by an active grid. Instantaneous velocity fields were collected over seven planes using particle image velocimetry (PIV). A center-plane (x-y) and six planes parallel to the floor (x-z) highlight the interaction and resulting vortex systems. Various jet-to-cross-flow velocity ratios, Rv, were collected for each plane, which allow for computation of mean statistics and Reynolds stresses. Analysis was focused in five stages: a) identification of differences in the development of the jet across various inflow conditions, b) analysis of the vortex systems through transport and critical points analysis, c) decomposition of the flow structures to identify and remove the highest-order contributions to turbulence kinetic energy and d) extraction of reduced order modeling closure terms and e) optimization of closure terms for the simplified one-dimensional model, Plumeria. These five stages provided a comprehensive description of the role of cross-flow turbulence on the development of JICF. Noteworthy findings include significant changes in wake recovery and the near-wake recirculation region that impacted near-field entrainment; increased entrainment for high cross-flow turbulence after the collapse of the potential core due to increased engulfment and viscous nibbling between turbulent fluids; the presence of shear layer and wake vortices through critical point analysis; and the absence of entrainment and shear layer expansion near the exit. Most importantly, the negligible entrainment near the exit and impact of small scale turbulent features that must be included for any specific model to yield reasonable predictions is highlighted. By laying the foundation for a more nuanced approach to JICF, it is possible to more precisely summarize the complex features observed in this work through simplified descriptions that can be of benefit to both engineering design and geophysical modeling.
Author:
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 193
Get Book Here
Book Description
A jet in cross flow (JICF) is examined experimentally by injecting a stream of air into crossing fluid with an aim into quantifying entrainment process and downstream evolution. The behavior of JICF is important to fields ranging from turbine-blade cooling to smokestack pollution and volcanic eruption dynamics. Existing simplified volcanic plume models are tested; most importantly, the near-field contributions of complex interconnected vortex systems, which present significant uncertainties because they assume negligible turbulence. While jets in irrotational cross-flow have been investigated, this analysis has focused on the interaction between a turbulent jet in low and highly turbulent cross-flow created by an active grid. Instantaneous velocity fields were collected over seven planes using particle image velocimetry (PIV). A center-plane (x-y) and six planes parallel to the floor (x-z) highlight the interaction and resulting vortex systems. Various jet-to-cross-flow velocity ratios, Rv, were collected for each plane, which allow for computation of mean statistics and Reynolds stresses. Analysis was focused in five stages: a) identification of differences in the development of the jet across various inflow conditions, b) analysis of the vortex systems through transport and critical points analysis, c) decomposition of the flow structures to identify and remove the highest-order contributions to turbulence kinetic energy and d) extraction of reduced order modeling closure terms and e) optimization of closure terms for the simplified one-dimensional model, Plumeria. These five stages provided a comprehensive description of the role of cross-flow turbulence on the development of JICF. Noteworthy findings include significant changes in wake recovery and the near-wake recirculation region that impacted near-field entrainment; increased entrainment for high cross-flow turbulence after the collapse of the potential core due to increased engulfment and viscous nibbling between turbulent fluids; the presence of shear layer and wake vortices through critical point analysis; and the absence of entrainment and shear layer expansion near the exit. Most importantly, the negligible entrainment near the exit and impact of small scale turbulent features that must be included for any specific model to yield reasonable predictions is highlighted. By laying the foundation for a more nuanced approach to JICF, it is possible to more precisely summarize the complex features observed in this work through simplified descriptions that can be of benefit to both engineering design and geophysical modeling.
Author: H. S. Chang
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 174
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Book Description
Author: Jin Tso
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: James Franklin Campbell
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 72
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Book Description
An investigation has been undertaken to develop a theoretical model of the incompressible jet injection process. The discharge of a turbulent jet into a cross flow was mathematically modeled by using an integral method which accounts for natural fluid mechanisms such as turbulence, entrainment, buoyancy, and heat transfer. The analytical results are supported by experimental data and demonstrate the usefulness of the theory for estimating the trajectory and flow properties of the jet for a variety of injection conditions. The capability of predicting jet flow properties, as well as two- and three- dimensional jet paths, was enhanced by obtaining the jet cross-sectional area during the solution of the conservation equations (a number of previous studies assume a specific growth for the area). Realistic estimates of temperature in the jet fluid were acquired by accounting for heat losses in the jet flow due to forced convection and to entrainment of free-stream fluid into the jet.
Author: Ann R. Karagozian
Publisher: Springer
ISBN: 3709127920
Category : Technology & Engineering
Languages : en
Pages : 304
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Book Description
Fundamental Non-Reactive Jets in Crossflow and Other Jet Systems; Background on Modeling, Dynamical Systems, and Control; Reactive Jets in Crossflow and Multiphase Jets; Controlled Jets in Crossflow and Control via Jet Systems;
Author: David Charles Thoman (Jr)
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This thesis summaries the results of an experimental investigation of the near-field behavior and physics of the round buoyant turbulent jet in crossflow. In particular, the study centers on the physics associated with entrainment and mixing phenomena of the jet with the goal of better understanding the trends of trajectory and dilution behavior. The experiments involved a downward discharge of cold nitrogen gas (at about $-$85$spcirc$C) from a cylindrical structure placed in a wind tunnel of horizontally flowing ambient air. The jet was mapped using thermocouple measurements. For the purpose of studying jet/crossflow and jet/wake interactions, fog-oil smoke was used to mark parcels of fluid in the crossflow upstream of the jet and in the wake flow downstream of the discharge structure. Time-averaged, smoke concentrations were gathered through an aspirated sampling probe in conjunction with a calibrated, optical aerosol monitor. Smoke distributions were also photographed. Experiments were performed for four different values for the crossflow-to-exit velocity ratio k, namely, k = 0.7, 1.3, 2.1, and 3.5. The results of the experiments yield a comprehensive picture of the near-field flow patterns, flow interactions, and flow-transport physics for a buoyant jet in crossflow. Key, phenomenologically distinct zones of flow which comprise the near-exit structure of the jet are identified. The flow patterns within these zones, and thus the structure of the near-exit jet, are found to be extremely dependent on the value of the velocity ratio. Flow interactions in this region establish flow patterns which have a pronounced influence on the downstream development of the jet. A method is developed to fully document the trajectory and dilution behavior of the jet with the key parameters of influence. Trajectory and dilution are found to correlate with two parameters, namely, the velocity ratio and the density-difference ratio. Finally, unsteady, large-scale mixing motions within the near-exit flow zones are documented. Distinct modes of large-scale mixing which are responsible for the rapid and extensive dispersion observed in the jet are revealed by this study.
Author: Jinjun Wang
Publisher: Cambridge University Press
ISBN: 1107161568
Category : Science
Languages : en
Pages : 293
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Book Description
Master the theory, applications and control mechanisms of flow control techniques.
Author: Arun K. Saha
Publisher: Springer
ISBN: 8132227433
Category : Technology & Engineering
Languages : en
Pages : 1638
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Book Description
This volume comprises the proceedings of the 42nd National and 5th International Conference on Fluid Mechanics and Fluid Power held at IIT Kanpur in December, 2014.The conference proceedings encapsulate the best deliberations held during the conference. The diversity of participation in the conference, from academia, industry and research laboratories reflects in the articles appearing in the volume. This contributed volume has articles from authors who have participated in the conference on thematic areas such as Fundamental Issues and Perspectives in Fluid Mechanics; Measurement Techniques and Instrumentation; Computational Fluid Dynamics; Instability, Transition and Turbulence; Turbomachinery; Multiphase Flows; Fluid‐Structure Interaction and Flow‐Induced Noise; Microfluidics; Bio‐inspired Fluid Mechanics; Internal Combustion Engines and Gas Turbines; and Specialized Topics. The contents of this volume will prove useful to researchers from industry and academia alike.
Author: Victor V. Kozlov
Publisher: Springer
ISBN: 3319269585
Category : Technology & Engineering
Languages : en
Pages : 135
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Book Description
Based on new information obtained on free microjets, this book explains the latest phenomena in flame evolution in the presence of a transverse acoustic field with round and plane propane microjet combustion. It gives an overview of recent experimental results on instability and dynamics of jets at low Reynolds numbers and provides the reader, step by step, with the milestones and recent advances in jet flow stability and combustion. Readers will also discover a clarification of the differences between top-hat and parabolic round and plane jet instability. Chapters demonstrate features of the interaction between jet and crossflow, and how experimental data testify to similarities of the perturbed flow patterns of laminar and turbulent round jets. A similar response of the jets to external acoustic oscillations is shown, as well as the peculiarities of the effect of a transverse acoustic field on downstream evolution of round and plane macro- and microjets. Basic features of round and plane, macro and micro jets' evolution affected by initial conditions at the nozzle outlet and by environmental perturbations are highlighted. Students of fluid mechanics will gain a solid foundation in hydrodynamic stability and combustion of subsonic jet flow and researchers will value the presentation of special aspects of instability and transition. The work treats both theoretical and practical facets, and it includes supplementary material such as PowerPoint multimedia notes based on results of laboratory scientific experiments.
Author: R. S. J. Sparks
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 608
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Book Description
Volcanic plumes, made up of material that has explosively erupted from a volcano, are of fundamental importance to volcanology because their deposits record the past activity of a volcano. They also pose a wide range of hazards to humans and can have significant environmental effects. This book integrates observation, theory, and experimental studies and contains recent research ideas and results.
