On Asymptotical & Numerical Analyses of Liquid Jets PDF Download
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Author: Muhammad Mohsin
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Muhammad Mohsin
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Arash Zandian
Publisher:
ISBN: 9781321094527
Category :
Languages : en
Pages : 139
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A numerical study of the temporal and spatial instabilities appearing on the interface of an annular liquid jet emerging from an orifice and flowing into a high pressure gas medium has been performed using Direct Numerical Simulation. The purpose of this study is to gain a better insight into the dominant mechanisms in the atomization of annular liquid jets during the start-up portion of the injection. The effects on the growth rate and wavelength of the emerging Kelvin-Helmholtz and Rayleigh-Taylor instabilities of various flow parameters have been investigated: the Reynolds and Weber numbers; fluids properties like gas-to-liquid density and viscosity ratios; and geometrical parameters involved in the problem such as thickness-to-diameter ratio of the liquid sheet. The Reynolds numbers used in this study are in the range from 3,000 to 30,000, and the Weber numbers are in the range of 6,000 up to 150,000. The convergence rate and length of the liquid jet has been also computed and compared for different cases. A characteristic convergence time has been proposed based on the obtained results. Use has been made of an unsteady axisymmetric code with a finite-volume solver of the Navier-Stokes equations for liquid streams and adjacent gas and a level-set method for the liquid/gas interface tracking. Two significant velocity reversals were detected on the axis of symmetry for all flow Reynolds numbers; the one closer to the nozzle exit being attributed to the recirculation zone, and the one farther downstream corresponding to the annular jet collapse on the centerline. The effects of different flow parameters on the location of these velocity reversals are studied. The results indicate that the convergence length and time increase significantly with the gas density and liquid viscosity and decrease with the liquid sheet thickness, while the effects of the gas viscosity and the surface tension are not so considerable. The range of unstable Kelvin-Helmholtz and Rayleigh-Taylor wavelengths have been also studied. The statistical data obtained from the numerical results show that, the average normalized wavelength of the KH instabilities decreases with the Reynolds and Weber numbers and the sheet thickness, and increases with the gas-to-liquid density ratio, and is independent of the viscosity ratio. The wavelength of the KH instabilities were observed to increase in time, except for the very thin liquid sheet, where the average KH wavelength oscillates between two values, indicating occurrence of different sheet breakup cycles. The sheet breakup times and lengths were reported up to the second sheet breakup, and it is shown that the later sheet breakups happen closer to the nozzle exit plane. The RT wavelengths tend to decrease during the start-up period of injection.
Author: Fereydoon Shokoohi
Publisher:
ISBN:
Category : Jets
Languages : en
Pages : 312
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Author: Sina Ghods
Publisher:
ISBN:
Category : Atomization
Languages : en
Pages : 86
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Book Description
The atomization of a liquid jet by a high speed cross-flowing gas has many applications such as gas turbines and augmentors. The mechanisms by which the liquid jet initially breaks up, however, are not well understood. Experimental studies suggest the dependence of spray properties on operating conditions and nozzle geometry. Detailed numerical simulations can offer better understanding of the underlying physical mechanisms that lead to the breakup of the injected liquid jet. In this work, detailed numerical simulation results of turbulent liquid jets injected into turbulent gaseous cross flows for different density ratios is presented. A finite volume, balanced force fractional step flow solver to solve the Navier-Stokes equations is employed and coupled to a Refined Level Set Grid method to follow the phase interface. To enable the simulation of atomization of high density ratio fluids, we ensure discrete consistency between the solution of the conservative momentum equation and the level set based continuity equation by employing the Consistent Rescaled Momentum Transport (CRMT) method. The impact of different inflow jet boundary conditions on different jet properties including jet penetration is analyzed and results are compared to those obtained experimentally by Brown & McDonell(2006). In addition, instability analysis is performed to find the most dominant insta- bility mechanism that causes the liquid jet to breakup. Linear instability analysis is achieved using linear theories for Rayleigh-Taylor and Kelvin- Helmholtz instabilities and non-linear analysis is performed using our flow solver with different inflow jet boundary conditions.
Author: Institute for Computer Applications in Science and Engineering
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 542
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 380
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1076
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Author: Gabriel R. Barrenechea
Publisher: Springer Nature
ISBN: 3030418006
Category : Mathematics
Languages : en
Pages : 254
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Book Description
This volume gathers papers presented at the international conference BAIL, which was held at the University of Strathclyde, Scotland from the 14th to the 22nd of June 2018. The conference gathered specialists in the asymptotic and numerical analysis of problems which exhibit layers and interfaces. Covering a wide range of topics and sharing a wealth of insights, the papers in this volume provide an overview of the latest research into the theory and numerical approximation of problems involving boundary and interior layers.
Author: Michael Renardy
Publisher: SIAM
ISBN: 9780898719413
Category : Mathematics
Languages : en
Pages : 113
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Book Description
This monograph is based on a series of lectures presented at the 1999 NSF-CBMS Regional Research Conference on Mathematical Analysis of Viscoelastic Flows. It begins with an introduction to phenomena observed in viscoelastic flows, the formulation of mathematical equations to model such flows, and the behavior of various models in simple flows. It also discusses the asymptotics of the high Weissenberg limit, the analysis of flow instabilities, the equations of viscoelastic flows, jets and filaments and their breakup, as well as several other topics.
