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.
Manipulation and Control of Jets in Crossflow
Author: Ann R. KaragozianPublisher: Springer Science & Business Media
ISBN: 9783211007532
Category : Technology & Engineering
Languages : en
Pages : 320
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;
Entrainment of a Hot Jet in a Crossflow
Author: Jin TsoTurbulent Jets and Plumes
Author: Joseph Hun-wei LeePublisher: Springer Science & Business Media
ISBN: 1461504074
Category : Science
Languages : en
Pages : 391
Book Description
Jets and plumes are shear flows produced by momentum and buoyancy forces. Examples include smokestack emissions, fires and volcano eruptions, deep sea vents, thermals, sewage discharges, thermal effluents from power stations, and ocean dumping of sludge. Knowledge of turbulent mixing by jets and plumes is important for environmental control, impact and risk assessment. Turbulent Jets and Plumes introduces the fundamental concepts and develops a Lagrangian approach to model these shear flows. This theme persists throughout the text, starting from simple cases and building towards the practically important case of a turbulent buoyant jet in a density-stratified crossflow. Basic ideas are illustrated by ample use of flow visualization using the laser-induced fluorescence technique. The text includes many illustrative worked examples, comparisons of model predictions with laboratory and field data, and classroom tested problems. An interactive PC-based virtual-reality modelling software (VISJET) is also provided. Engineering and science students, researchers and practitioners may use the book both as an introduction to the subject and as a reference in hydraulics and environmental fluid mechanics.
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.
Analysis of a Jet in a Subsonic Crosswind
Author: A Method for Estimating Jet Entrainment Effects on Nozzle-afterbody Drag
Author: R. C. BauerPublisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 30
Book Description
A highly simplified analysis was used to derive an expression for estimating the induced afterbody drag caused by the turbulent jet-mixing process. The approach estimates the induced velocity produced by the jet-mixing process and uses small perturbation concepts to estimate the resulting pressure change on the afterbody surface from which the induced afterbody drag coefficient is obtained. The theoretical induced afterbody drag (entrainment drag) is combined with the maximum jet plume diameter blockage condition to form a correlation method that accounts for the effect of jet area ratio, exit angle, total temperature, molecular weight and ratio of specific heats for a given external stream Mach number, Reynolds number, and afterbody geometry. For verification, the correlation method was used to predict the drag of an H2 and C2H4 jet from the measured drag of an N2 jet and to predict the drag of a hot jet from the measured drag of a cold jet for both the 15- and 25-deg AGARD afterbody configurations in the Mach number range from 0.6 to 1.5. The average accuracy of the correlation method is better than 10% for both afterbody configurations and is 40 to 50 % more accurate than a correlation method based only on the blockage parameter. A brief numerical study indicates that the major parameter which correlates the jet entrainment effect is the product of the jet gas constant and total temperature. (Author).
The Entrainment and Mixing of a Round Buoyant Turbulent Jet in Crossflow
Author: David Charles ThomanPublisher:
ISBN:
Category :
Languages : en
Pages : 622
Book Description
Author: A. O. Demuren