Download or read book Turbulent Jets in the Presence of a Turbulent Ambient written by Amirhossein Afrooz and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Turbulent mixing, which leads to dilution or chemical reactions (including combustion) at a molecular level, is studied using a passive scalar. Khorsandi (2013) and Perez-Alvarado (2016) studied the velocity and concentration fields of an axisymmetric turbulent jet in zero mean flow, respectively, in a quiescent and turbulent ambient. The aim of the present study is to extend this work observing a turbulent jet released into a nearly homogeneous isotropic turbulent background with negligible mean flow created with a random jet array. The characteristic of the jet in a turbulent background flow is compared to that released into a quiescent background. Planar laser induced fluorescence (PLIF) is used for flow visualization and to quantify concentrations in cross-sections of turbulent jets with Reynolds numbers of 5800 and 10600 at axial distances between x/D of 20 and 70. The data was post-processed using MATLAB codes. Flow visualisation shows that the jet cross-section has greater variation in position and shape when released into a turbulent ambient, due to the larger eddies of the turbulence distorting the jet path and the smaller eddies distorting the jet cross-section, until at some downstream distance the turbulence results in the breakup of the jet (zero mean jet velocity). The increased variability of the jet is seen in time traces of the centreline concentration. The jet cross-sections are spatially averaged to determine the rate of decrease of the concentration and increase of the jet half width with axial distance. Normalized centreline concentration varies with normalized axial distance as x-1 in a quiescent ambient and with x-1.7 for the jet with Re = 10600 and x-2.1 for the jet with Re = 5800 in the turbulent ambient. The normalized jet half width varies with normalized axial distance as x1 in a quiescent ambient and with x1.2 for jet Re = 10600 and x1.4 for jet Re = 5800 in the turbulent ambient. The position of the centre of mass of the jet cross-sections indicated a greater meandering of the jet path with downstream distance (Re = 10600). The radius of gyration of the jet was used to identify the growth in width of the cross-section independent of the meandering of the jet path. The normalized radius of gyration of the jet varied as x1.8 for the jet released in both quiescent and turbulent ambient, however the magnitude was greater in the turbulent ambient with a greater increase for the lower Reynolds number jet. The downstream evolution of the cross-sectional shape factor also indicated the greater disruption of the cross-section in the turbulent ambient. Lastly, the decay in the time averaged centreline concentration was compared to that of the centreline velocity and was found to decrease more gradually in the turbulent ambient. In summary, the turbulence in the ambient progressively breaks up the jet structure and distorts the jet path resulting in a faster rate of decay of the jet, which is greater for jets with lower Reynolds number." --

Download or read book Turbulent Jets written by N. Rajaratnam and published by Elsevier. This book was released on 1976-01-01 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent Jets

Download or read book A Numerical Study of Confined Turbulent Jets written by and published by . This book was released on 1993 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Theory of Turbulent Jets written by G. N. Abramovich and published by Mit Press. This book was released on 1963 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt: The author's first monograph on turbulent jets, in 1936, dealt solely with a free submerged jet. Since that time, the theory of the turbulent jet has been developed in many published works both in the USSR and abroad: it has been enriched with a large amount of experimental material and has been applied in many new fields of engineering. In the last 10 years very substantial progress has been made, and it has now become possible to go beyond the free submerged jet and to solve the problem of a jet in a stream of fluid, to take into account the interaction between the jet and solid walls, to ascertain the relationship between the contour of the jet and the ratio of its density to the density of the surrounding medium, and to establish the characteristic features of a supersonic jet. This monograph contains the results of further research by the author and his colleagues, as well as a critical reappraisal of the more important theoretical and experimental data published by other investigators. The first section deals with the theory of a turbulent jet of incompressible fluid. It gives a systematic analysis of numerous experimental data on velocity profiles, temperature, and the impurity concentration, as well as the outlines of the turbulent mixing lone. The second section sets forth the theory of turbulent gas jets, including strongly preheated and supersonic jets. The theory of free turbulence in a gas, suitable in principle for any degree of compressibility, is revised, and the equations are derived for motion and heat exchange in the boundary layer of a jet at very high temperature. The third section solves several problems of the spreading of jets in finite and semifinite space, and the fourth section describes various applications of the theory of jets, many of which are reported for the first time or have been significantly revised.

Download or read book Interaction of a Buoyant Turbulent Planar Jet with a Co flowing Wind written by Milton M. Klein and published by . This book was released on 1975 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The classic theory of buoyant motion of a free planar heated jet in still air is extended to account for environmental winds from the same direction as the jet, that is, co-flowing winds. The model is applicable for wind and jet velocities up to 100 m/sec, and jet temperatures up to three times the ambient. Calculations are made for initial jet velocities of 5 and 20 m/sec and temperature excesses, relative to ambient temperature, of 0.3 and 1. For light winds relative to the initial jet velocity the vertical velocity and centerline trajectory of the plume rise rapidly with distance from the jet source. This is similar to that found with the classic theory for still air. As the wind speed approaches the initial jet velocity, the rise of the jet plume with distance from the source is much more gradual. For all wind speeds, the axial jet velocity and temperature decrease rapidly with distance from the jet source, until they become almost constant at short distances downstream. A similarity rule is derived which preserves dynamic similarity in scaling from a given system to another system. For low wind speeds the procedure is close to that based on constant Froude number. (Author).

Download or read book The Theory of Turbulent Jets written by Genrikh Naumovich Abramovich and published by . This book was released on 1963 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Numerical Study of Confined Turbulent Jets written by J. Zhu and published by . This book was released on 1993 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A numerical investigation is reported of turbulent incompressible jets confined in two ducts, one cylindrical and the other conical with a 5 degree divergence. In each case, three Craya-Curtet numbers are considered which correspond, respectively, to flow situations with no moderate and strong recirculation. Turbulence closure is achieved by using the k-epsilon model and a recently proposed realizable Reynolds stress algebraic equation model that relates the Reynolds stresses explicitly to the quadratic terms of the mean velocity gradients and ensures the positiveness of each component of the turbulent kinetic energy. Calculations are carried out with a finite-volume procedure using boundary-fitted curvilinear coordinates. A second-order accurate, bounded convection scheme and sufficiently fine grids are used to prevent the solutions from being contaminated by numerical diffusion. The calculated results are compared extensively with the available experimental data. It is shown that the numerical methods presented are capable of capturing the essential flow features observed in the experiments and that the realizable Reynolds stress algebraic equation model performs much better than the k-epsilon model for this class of flows of great practical importance.

Download or read book Turbulent Buoyant Jets Into Statified Or Flowing Ambient Fluids written by Loh-Nien Fan and published by . This book was released on 1967 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulent Jets and Plumes written by Joseph Hun-wei Lee and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Characteristics of 3D Turbulent Jets in Crossflow written by A. O. Demuren and published by . This book was released on 1991 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experiments on Confined Turbulent Jets in Cross Flow written by Yasuhiro Kamotani and published by . This book was released on 1974 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characteristics of Three dimensional Turbulent Jets written by Choudary Rama Krishna Bobba and published by . This book was released on 1979 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Structure of Turbulent Jets written by Emil Sekula and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Dynamics of an Axisymmetric Turbulent Jet and of a Passive Scalar Patch in Ambient Turbulence Interpreted from the Passive Scalar Field Statistics written by Rana Sahebjam and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The passive scalar field of an axisymmetric turbulent jet and an isokinetic jet in an approximately homogeneous isotropic turbulence (HIT) with negligible mean flow is studied experimentally. The present research builds on that of Khorsandi et al. 2013 and Perez-Alvarado 2016, who studied the velocity field and the passive scalar field of an axisymmetric turbulent jet in a turbulent ambient, respectively. The primary objective is to deduce the jet structure, and to study the jet mixing in the HIT ambient by following the meandering path of the jet, i.e. conditional on the jet centroid. The secondary objective, complementing the first, is to study the diffusion of a momentumless patch of a passive scalar in the HIT ambient.The effect of a turbulent ambient on the dynamics and mixing of the passive scalar field of an axisymmetric turbulent jet is investigated. The experiments were conducted either in a quiescent or a turbulent ambient. The turbulent ambient was generated by a random jet array to achieve an approximately zero-mean-flow HIT ambient in the measurement plane. Two jet Reynolds numbers of Re = 5800 and 10600 were studied. Planar laser-induced fluorescence was used to measure the concentrations of the passive scalar dye (Sc = 2000) at orthogonal cross-sections of the jet at axial distances of x/d = 20, 30, 40, 50, 60. The statistics of the passive scalar field were conditioned on the jet centroid and were compared to the Eulerian statistics and to those of the jet in a quiescent ambient. The use of the centroidal analysis allowed the structure of the jet in the HIT ambient to be deduced, for which a two-region model was proposed. In the first region, following the developing region of the jet, the ambient turbulence progressively disrupts the jet structure and results in a faster concentration decay compared to the quiescent ambient. At a critical downstream distance, where the relative turbulence intensity between the ambient and the jet (ξ = urms,HIT/ urms,jet ) exceeds 0.5, the HIT ambient has destroyed the jet structure and the second region starts. In the second region, the turbulent diffusion is the only mechanism to transport the passive scalar field. The first-order centroidal statistics of the scalar field show self-similarity and self-preservation before jet break-up. The width of the jet is larger in the HIT ambient compared to that in a quiescent ambient and grows with axial distance but remains unchanged beyond jet break-up. Using the present passive scalar data and the velocity data from Khorsandi et al. 2013, it is argued that the momentum-driven entrainment of the jet in the HIT ambient is reduced compared to that in a quiescent ambient, and that the entrainment ceases beyond the jet break-up. The entrainment of the smaller scales of the ambient turbulence leads to a wider range of centerline concentrations and rms concentrations within the jet, and they are hypothesized to increase local concentration gradients and reduce the jet mixing.Diffusion of a patch of a passive scalar in the HIT ambient is studied. A high-Sc number passive scalar dye (Sc = 2500) is released isokinetically from a large diameter jet (d = 29.97 mm), and an orthogonal view of the passive scalar field is obtained using planar laser-induced fluorescence. The temporal evolution of the scalar patch is due to molecular diffusion and to turbulent diffusion in a quiescent ambient and in the HIT ambient, respectively. Time-averaged statistics of the passive scalar field are assessed at t = 0.2, 1, 1.8, 2.6, 3.4 s using a centroidal analysis. The mean concentration decays quickly and the rms concentration increases within the scalar patch. Compared to the quiescent ambient case, a wider range of the concentrations is present at the centroid of the scalar field. The size of the scalar patch increases with time, which is attributed to an increasing turbulent diffusivity for times shorter than the integral time scale of the turbulence"--

Download or read book A Turbulent Equatorial Jet written by Robert R. Long and published by . This book was released on 1962 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Prediction of Radially Spreading Turbulent Jets written by M. R. Malin and published by . This book was released on 1987 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Entrainment by Turbulent Jets of Air written by James Roger Connell and published by . This book was released on 1973 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: