scholarly journals On the near-field interfaces of homogeneous and immiscible round turbulent jets

2020 ◽  
Vol 889 ◽  
Author(s):  
Eric Ibarra ◽  
Franklin Shaffer ◽  
Ömer Savaş
Keyword(s):  
Near Field ◽  
Turbulent Jets ◽  
Image Position

scholarly journals Instability wave models for the near-field fluctuations of turbulent jets

2011 ◽  
Vol 689 ◽  
pp. 97-128 ◽  
Author(s):  
K. Gudmundsson ◽  
Tim Colonius
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Microphone Array ◽  
Near Field ◽  
Turbulent Jets ◽  
Instability Wave ◽  
Mean Flow ◽  
Velocity Fluctuations ◽  
The Mean ◽  
Scale Structures

AbstractPrevious work has shown that aspects of the evolution of large-scale structures, particularly in forced and transitional mixing layers and jets, can be described by linear and nonlinear stability theories. However, questions persist as to the choice of the basic (steady) flow field to perturb, and the extent to which disturbances in natural (unforced), initially turbulent jets may be modelled with the theory. For unforced jets, identification is made difficult by the lack of a phase reference that would permit a portion of the signal associated with the instability wave to be isolated from other, uncorrelated fluctuations. In this paper, we investigate the extent to which pressure and velocity fluctuations in subsonic, turbulent round jets can be described aslinearperturbations to the mean flow field. The disturbances are expanded about the experimentally measured jet mean flow field, and evolved using linear parabolized stability equations (PSE) that account, in an approximate way, for the weakly non-parallel jet mean flow field. We utilize data from an extensive microphone array that measures pressure fluctuations just outside the jet shear layer to show that, up to an unknown initial disturbance spectrum, the phase, wavelength, and amplitude envelope of convecting wavepackets agree well with PSE solutions at frequencies and azimuthal wavenumbers that can be accurately measured with the array. We next apply the proper orthogonal decomposition to near-field velocity fluctuations measured with particle image velocimetry, and show that the structure of the most energetic modes is also similar to eigenfunctions from the linear theory. Importantly, the amplitudes of the modes inferred from the velocity fluctuations are in reasonable agreement with those identified from the microphone array. The results therefore suggest that, to predict, with reasonable accuracy, the evolution of the largest-scale structures that comprise the most energetic portion of the turbulent spectrum of natural jets, nonlinear effects need only be indirectly accounted for by considering perturbations to the mean turbulent flow field, while neglecting any non-zero frequency disturbance interactions.

Modeling and Analytical Solution of Near-Field Entrainment in Suddenly Started Turbulent Jets

AIAA Journal ◽  
2019 ◽  
Vol 57 (5) ◽  
pp. 1877-1884 ◽  
Author(s):  
M. E. Feyz ◽  
M. R. Nalim ◽  
V. R. Hasti ◽  
J. P. Gore
Keyword(s):  
Analytical Solution ◽  
Near Field ◽  
Turbulent Jets

scholarly journals Jet-installation noise and near-field characteristics of jet–surface interaction

2020 ◽  
Vol 895 ◽  
Author(s):  
L. Rego ◽  
F. Avallone ◽  
D. Ragni ◽  
D. Casalino
Keyword(s):  
Near Field ◽  
Surface Interaction ◽  
Image Position

scholarly journals The Snomipede: A parallel platform for scanning near-field photolithography

2011 ◽  
Vol 26 (24) ◽  
pp. 2997-3008 ◽  
Author(s):  
Ehtsham ul-Haq ◽  
Zhuming Liu ◽  
Yuan Zhang ◽  
Shahrul A. Alang Ahmad ◽  
Lu Shin Wong ◽  
...  
Keyword(s):  
Near Field ◽  
Parallel Platform ◽  
Image Position

Abstract

Coherent structures in the near-field of swirling turbulent jets: A tomographic PIV study

2018 ◽  
Vol 70 ◽  
pp. 363-379 ◽  
Author(s):  
Sergey V. Alekseenko ◽  
Sergey S. Abdurakipov ◽  
Mikhail Y. Hrebtov ◽  
Mikhail P. Tokarev ◽  
Vladimir M. Dulin ◽  
...  
Keyword(s):  
Coherent Structures ◽  
Near Field ◽  
Turbulent Jets ◽  
Tomographic Piv

PIV Study of the Near-Field Region of a Turbulent Round Jet

2010 ◽  
Author(s):  
Ivana M. Milanovic ◽  
Khaled J. Hammad
Keyword(s):  
Large Scale ◽  
Near Field ◽  
Flow Characteristics ◽  
Turbulent Jets ◽  
Reynolds Numbers ◽  
Field Region ◽  
Initial Development ◽  
Number Range ◽  
Developed Turbulence ◽  
Fully Developed Turbulent Flow

Turbulent jets have been extensively studied in the past due to their fundamental importance and wide spread usage in numerous industrial processes to enhance momentum, heat and mass transfer. Most previous work focused on the far-field or self-similar region of the flow. However, the initial development region, where the flow is dominated by streamwise and large-scale, Kelvin-Helmholtz-type, structures, received far less attention. In the current study, Particle Image Velocimetry (PIV) was used to obtain reliable statistics in the near-field region of a turbulent submerged jet. The jet issued from an 84 diameter, D, long pipe which ensured fully-developed turbulent flow conditions at the outlet. The two-dimensional flow field in the plane containing the jet axis was measured in the initial 8D region, for three Reynolds numbers: 14,602, 19,135, and 24,685. The selected Reynolds numbers overlap with the previously identified critical Reynolds number range, 10,000–20,000, where flow characteristics of a jet undergo a dramatic transition to a much more chaotic and well-mixed state or fully developed turbulence.

scholarly journals A Study of RANS Turbulence Models in Fully Turbulent Jets: A Perspective for CFD-DEM Simulations

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 271
Author(s):  
Dustin Weaver ◽  
Sanja Mišković
Keyword(s):  
Stokes Equations ◽  
Near Field ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Turbulent Jets ◽  
Navier Stokes ◽  
Straight Tube ◽  
Developed Turbulence ◽  
Similar Work ◽  
Tube Geometry

This paper presents an analysis of linear viscous stress Favre averaged turbulence models for computational fluid dynamics (CFD) of fully turbulent round jets with a long straight tube geometry in the near field. Although similar work has been performed in the past with very relevant solutions, considerations were not given for the issues and limitations involved with coupling between an Eulerian and Lagrangian phase, such as in fully two-way coupled CFD-DEM. These issues include limitations on solution domain, mesh cell size, wall modelling, and momentum coupling between the two phases in relation to the particles size. Therefore, within these considerations, solutions are provided to the Navier–Stokes equations with various turbulence models using a three-dimensional wedge long straight tube geometry for fully developed turbulence flow. Simulations are performed with a Reynolds number of 13,000 and 51,000 using two different tube diameters. It is found that a modified k-ε turbulence model achieved the most agreeable results for both the velocity and turbulent flow fields between these two flow regimes, while a modified k-ω SST/BSL also provided suitable results.

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