Author: H. S. ChangPublisher:
ISBN:
Category : Jets
Languages : en
Pages : 174
Book Description
Analysis of an Entrainment Model of the Jet in a Crossflow
Author: H. S. ChangEntrainment Processes for a Jet in Cross-Flow
Author: Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 193
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.
Analysis of the Injection of a Heated Turbulent Jet Into a Cross Flow
Author: James Franklin CampbellPublisher:
ISBN:
Category : Jets
Languages : en
Pages : 72
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.
Entrainment of a Hot Jet in a Crossflow
Author: Jin TsoThe Entrainment and Mixing of a Round Buoyant Turbulent Jet in Cross-flow
Author: David Charles Thoman (Jr)Publisher:
ISBN:
Category :
Languages : en
Pages :
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.
Scientific and Technical Aerospace Reports
Author: Manipulation and Control of Jets in Crossflow
Author: Ann R. KaragozianPublisher: Springer
ISBN: 3709127920
Category : Technology & Engineering
Languages : en
Pages : 304
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;
Volcanic Plumes
Author: R. S. J. SparksPublisher:
ISBN:
Category : Nature
Languages : en
Pages : 608
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.
Analysis of a Jet in a Subsonic Crosswind
Author: Analysis of the Injection of a Heated Turbulent Jet Into a Cross Flow
Author: James Franklin CampbellPublisher:
ISBN:
Category : Jets
Languages : en
Pages : 70
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.