Subsonic Round and Plane Jets in the Transversal Acoustic Field

2010 ◽  
Vol 5 (2) ◽  
pp. 28-42
Author(s):  
Viktor V. Kozlov ◽  
Genrich R. Grek ◽  
Yuriy A. Litvinenko ◽  
Grigory V. Kozlov ◽  
Maria V. Litvinenko
Keyword(s):  
Acoustic Field ◽  
Experimental Studies ◽  
Field Vector ◽  
Field Energy ◽  
Stream Velocity ◽  
Acoustic Effect ◽  
Plane Jets ◽  
Splitting Angle ◽  
Plane Jet ◽  
Downstream Development

Results of the experimental studies of the subsonic round and plane both the macro and micro-jets are reported. The new phenomenon associated with transformation of the round micro-jets into the plane micro-jets under effect of a transversal acoustic field is revealed. It is shown, that its downstream development is determined by the sinusoidal instability mechanism of the plane jet. The disintegration phenomenon of the micro-jets on two jets developing separately from each other is revealed. It is found, that two new micro-jets are spreaded under a definite angle to each other and subjected by high-frequency secondary instability. It is shown, that sinusoidal instability of a plane jet is saved for macro and microjets both with acoustic and without acoustic effect. It is found, that the pseudo plane micro-jet at the presence of an acoustic field demonstrates presence in it of the vortex structures and dependence of the jet splitting angle from the frequency acoustic. The new phenomenon, so-called twist of a plane of a micro-jet on its edges in direction of the stream velocity vector created by a transversal acoustic field is revealed. It is shown, that process of the micro-jet twist result in a stupor of the jet downstream development and delay of its turbulisation. It is found, that sinusoidal instability of the round microjet depends on a direction of the acoustic field vector while the plane micro-jet does not depend. It is shown, that the new phenomena detected during investigations of a development both the round and plane micro-jet are stipulated by commensurability of the transversal acoustic field energy with the micro-jets energy.

Turbulent characteristics of a shallow wall-bounded plane jet: experimental implications for river mouth hydrodynamics

2009 ◽  
Vol 627 ◽  
pp. 423-449 ◽  
Author(s):  
JOEL C. ROWLAND ◽  
MARK T. STACEY ◽  
WILLIAM E. DIETRICH
Keyword(s):  
Large Scale ◽  
Experimental Studies ◽  
River Mouth ◽  
Experimental Results ◽  
Stream Velocity ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Turbulent Structures ◽  
Turbulent Characteristics ◽  
Plane Jet

Jets arising from rivers, streams and tidal flows entering still waters differ from most experimental studies of jets both in aspect ratio and in the presence of a solid bottom boundary and an upper free surface. Despite these differences, the applicability of experimental jet studies to these systems remains largely untested by either field or realistically scaled experimental studies. Here we present experimental results for a wall-bounded plane jet scaled to jets created by flow discharging into floodplain lakes. A characteristic feature of both our prototype and experimental jets is the presence of large-scale meandering turbulent structures that span the width of the jets. In our experimental jets, we observe self-similarity in the distribution of mean streamwise velocities by a distance of six channel widths downstream of the jet outlet. After a distance of nine channel widths the velocity decay and the spreading rates largely agree with prior experimental results for plane jets. The magnitudes and distributions of the cross-stream velocity and lateral shear stresses approach self-preserving conditions in the upper half of the flow, but decrease in magnitude, and deviate from self-preserving distributions with proximity to the bed. The presence of the meandering structure has little influence on the mean structure of the jet, but dominates the jet turbulence. A comparison of turbulence analysed at time scales both greater than and less than the period of the meandering structure indicates that these structures increase turbulence intensities by 3–5 times, and produce lateral shear stresses and momentum diffusivities that are one and two orders of magnitude greater, respectively, than turbulence generated by bed friction alone.

The Features of Hydrogen Combustion in Round and Plane Microjet in the Transverse Acoustic Field, and Comparison with the Results Propane Combustion

2014 ◽  
Vol 9 (1) ◽  
pp. 79-86
Author(s):  
Viktor Kozlov ◽  
Genrich Grek ◽  
Oleg Korobeinichev ◽  
Yuriy Litvinenko ◽  
Andrey Shmakov
Keyword(s):  
Acoustic Field ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Hydrogen Combustion ◽  
Diffusion Combustion ◽  
Propane Combustion ◽  
Experimental Conditions ◽  
Transverse Acoustic ◽  
Plane Jets ◽  
Oscillation Process

Experimental studies of the hydrogen combustion in the round and plane microjet in cross acoustic field at low Reynolds numbers are presented. The results are compared with the results obtained during the combustion of propane, studied earlier in the same experimental conditions. It is shown that the lifted flame of propane at diffusion combustion in a round microjet, under the influence of a transverse acoustic field, subject to bifurcation. This phenomenon is associated with the development of a sinusoidal oscillation process occurring under the influence of a transverse acoustic field. For the case of hydrogen combustion of plane microjet to lift the flame also failed, but the bifurcation effect is manifested at velocity close to 450 m/s. In this case acoustic disturbances generated by the jet, and a sinusoidal instability is typical for the plane jets

Heat Exchange Characteristics in Heat Supply and Heat Removal Parts of a Nonisothermal Circuit, Including Temperature and Velocity Fields in a HLMC Flow, for Controlled Impurity Content

2009 ◽  
Author(s):  
O. O. Novozhilova ◽  
A. V. Beznosov ◽  
S. Yu. Savinov ◽  
M. A. Antonenkov
Keyword(s):  
Heat Exchange ◽  
Oxygen Content ◽  
Velocity Structure ◽  
Experimental Studies ◽  
Heat Removal ◽  
Impurity Content ◽  
Stream Velocity ◽  
Carrier Stream ◽  
Temperature And Velocity Fields ◽  
Annular Clearance

Results of the experimental studies of the heat exchange to the lead heat-transfer agent in the annular clearance in the circulation contour with the controlled and operated processes of mass exchange and mass transfer of the oxygen content are presented. And results of experimental research of lead-bismuth heat-carrier stream velocity structure at a varied content of oxygen content are presented.

The Prediction of Velocity Distribution of Plate Jet with a EMMS Model

2015 ◽  
Vol 799-800 ◽  
pp. 629-634
Author(s):  
Ke Zhi Yu ◽  
Hai Zhang ◽  
Yan Ling Liu
Keyword(s):  
Velocity Distribution ◽  
Viscous Dissipation ◽  
Energy Minimization ◽  
Scale Model ◽  
Stability Conditions ◽  
Multi Scale ◽  
Plane Jets ◽  
The Stability ◽  
Plane Jet

The energy minimization multi-scale model is applied to the plane jet. The stability conditions of plane jets is adopted to predict the velocity distribution of plane jet. When the ratio of total dissipation to viscous dissipation tends to the maximum is used as the optimization condition and entrancement factor is considered as a constant, the Gauss velocity distribution can be concluded in the plane jet.

Elliptic jets. Part 1. Characteristics of unexcited and excited jets

1989 ◽  
Vol 208 ◽  
pp. 257-320 ◽  
Author(s):  
Fazle Hussain ◽  
Hyder S. Husain
Keyword(s):  
Shear Layer ◽  
Initial Conditions ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Vortical Structures ◽  
Aspect Ratios ◽  
Curvature Variation ◽  
Section Shape ◽  
Plane Jets ◽  
Circular Jets

This paper summarizes experimental studies of incompressible elliptic jets of different aspect ratios and initial conditions, and effects of excitations at selected frequencies and amplitudes. Elliptic jets are quite different from the extensively studied plane and circular jets - owing mainly to the fact that the azimuthal curvature variation of a vortical structure causes its non-uniform self-induction and hence complex three-dimensional deformation. Such deformation, combined with properly selected excitation can substantially alter entrainment and other turbulence phenomena, thus suggesting preference for the elliptic shape in many jet applications. The dominance of coherent structures in the jet far field is evident from the finding that switching over of the cross-section shape continues at least up to 100 equivalent diameters De. The locations and the number of switchovers are strongly dependent on the initial condition, on the aspect ratio, and, when excited, on the Strouhal number and the excitation level. We studied jets with constant exit momentum thickness θe, all around the perimeter, thus separating the effects of azimuthal variations of θe, (typical of elliptic jets) and of the shear-layer curvature. Also investigated are the instability characteristics, and enhanced entrainment caused by bifurcation as well as pairing of vortical structures. We discuss shear-layer and jet- column domains, and find the latter to be characterized by two modes : the preferred mode and the stable pairing mode - similar to those found in circular jets -both modes scaling on the newly-defined lengthscale De. The paper documents some time- average measurements and their comparison with those in circular and plane jets.

On the influence of coherent structures upon interscale interactions in turbulent plane jets

2002 ◽  
Vol 473 ◽  
pp. 103-145 ◽  
Author(s):  
C. B. da SILVA ◽  
O. MÉTAIS
Keyword(s):  
Kinetic Energy ◽  
Coherent Structures ◽  
Energy Transport ◽  
Local Equilibrium ◽  
Coherent Vortices ◽  
Free Shear Layers ◽  
Plane Jets ◽  
Energy Exchanges ◽  
Turbulent Plane ◽  
Plane Jet

The influence of the coherent structures on grid/subgrid-scale (GS/SGS) interactions in free shear layers is analysed through the application of a top-hat filter to several plane jet direct numerical simulations (DNS). The Reynolds number based on the plane jet inlet slot width is Reh = 3000. The study deals with energy containing (Kelvin–Helmholtz) and inertial range (streamwise) vortices, from the far field of the turbulent plane jet. The most intense kinetic energy exchanges between GS and SGS occur near these structures and not randomly in the space. The GS kinetic energy is dominated by GS advection and GS pressure/velocity interactions which appear located next to the Kelvin–Helmholtz rollers. Surprisingly, GS/SGS transfer is not very well correlated with the coherent vortices and GS/SGS diffusion plays an important role in the local dynamics of both GS and SGS kinetic energy. The so-called ‘local equilibrium assumption’ holds globally but not locally as most viscous dissipation of SGS kinetic energy takes place within the vortex cores whereas forward and backward GS/SGS transfer occurs at quite different locations. Finally, it was shown that SGS kinetic energy advection may be locally large as compared to the other terms of the SGS kinetic energy transport equation.

scholarly journals Performance of spray nozzles in land applications with high speed

2012 ◽  
Vol 32 (6) ◽  
pp. 1126-1132 ◽  
Author(s):  
Samir E. Zaidan ◽  
Casimiro D. Gadanha Jr ◽  
Marco A. Gandolfo ◽  
Cristiano O. Pontelli ◽  
Walter W. Mosquini
Keyword(s):  
High Speed ◽  
Uv Light ◽  
Coverage Area ◽  
Application Efficiency ◽  
Fluorescent Pigment ◽  
Plane Jets ◽  
Twin Jets ◽  
Soybean Plants ◽  
Displacement Speed ◽  
Plane Jet

The aim of this study was to evaluate different spray nozzles for land applications in high speed on the coverage and deposit in soybean plants pulverization. It was evaluated the AXI 110 04 plane jet nozzles operated at speed of 4.17m.s-1 (control), the grey APE and the AXI 110 08 plane jets, and the TD HiSpeed 110 06 and AXI TWIN 120 06 twin jets, at speed of 9.72m.s-1. The application volume was fixed in 120L ha-1. The application efficiency was evaluated by two different methods: analysis of the coverage area using fluorescent pigment and UV light and analysis of deposits through the recovery and quantification of FD&C N°1 brilliant blue marker by spectrophotometry. Both analyses were done in samples collected from top, middle and bottom parts of the plants. The spray nozzles showed differences in coverage and deposit pattern, so in the top part, the coverage was increased with smaller drops and the deposits were increased with medium drops. In the other parts of the plants, there were no statistical differences between the treatments for both coverage and deposits. The displacement speed did not influence the application efficiency for nozzles with the same drop pattern, and the obtained spray coverage and deposits at the medium and bottom parts of the plants were less than 50% of that found at the top of the soybean plants.

Contributions to the theory of sound production by vortex-airfoil interaction, with application to vortices with finite axial velocity defect

1988 ◽  
Vol 420 (1858) ◽  
pp. 157-182 ◽  
Keyword(s):  
Axial Velocity ◽  
Sound Production ◽  
Field Energy ◽  
Small Scale ◽  
Stream Velocity ◽  
Destructive Interference ◽  
Trailing Edge ◽  
Core Diameter ◽  
Velocity Defect ◽  
The Core

An analysis is made of the sound produced when a field of vorticity is cut by an airfoil in low-Mach-number flow. A general formula is given for the acoustic pressure when the airfoil is rigid and the chord is acoustically compact. This expresses the radiation in terms of an integral over the region occupied by the vorticity; the integrand contains factors describing the influence of the thickness, twist and camber of the airfoil. Explicit analytical results are derived for a rectilinear vortex, having small core diameter and finite axial velocity defect, which is ‘chopped’ by a non-lifting airfoil of large aspect ratio. The acoustic signature generally comprises two components, which are associated with the axial and azimuthal vorticity, the latter being determined by the velocity defect distribution within the core. Sound is generated predominantly when the core is in the neighbourhoods of the leading and trailing edges. The contribution from the trailing edge is usually small, however, because of destructive interference between sound produced by edge-diffraction of near-field energy of the vortex and that produced by vorticity shed into the wake of the airfoil to satisfy the unsteady Kutta condition that the pressure and velocity should be bounded at the edge. When the shed vorticity is assumed to convect at the same mean stream velocity as the impinging vortex, the interference is predicted to be complete, and no trailing edge sound is generated. If the shed vorticity is taken to convect at a reduced, ‘near-wake’ velocity, which might be appropriate for small-scale structures comparable in size to the diameter of the vortex core, a small but non-negligible pressure pulse is radiated from the trailing edge. A tentative comparison with experiment appears to confirm the presence of this trailing-edge pulse.

Round and plane jets in a transverse acoustic field

2011 ◽  
Vol 20 (3) ◽  
pp. 272-289 ◽  
Author(s):  
V. V. Kozlov ◽  
G. R. Grek ◽  
Yu. A. Litvinenko ◽  
G. V. Kozlov ◽  
M. V. Litvinenko
Keyword(s):  
Acoustic Field ◽  
Transverse Acoustic ◽  
Plane Jets

Two parallel plane jets: Comparison of the performance of three turbulence models

1998 ◽  
Vol 212 (6) ◽  
pp. 379-391 ◽  
Author(s):  
J C S Lai ◽  
A Nasr
Keyword(s):  
Laser Doppler Anemometry ◽  
Turbulence Models ◽  
Domain Size ◽  
Flow Region ◽  
Quantitative Agreement ◽  
Parallel Plane ◽  
Computational Domain ◽  
Recirculation Flow ◽  
Plane Jets ◽  
Plane Jet

There have been many investigations in the literature to examine the performance of different turbulence models in predicting flow over backward-facing steps where the flow is bounded by solid boundaries. However, the evaluation of different turbulence models in predicting free shear layers with no solid boundaries, such as two parallel plane jets, is limited. In this paper, the velocity field of two parallel plane jets with a small nozzle separation ratio of s/ w = 4:25 determined by laser Doppler anemometry (LDA) is first presented. These experimental results are used to examine the performance of three turbulence models (i.e. k - ɛ, RNG k - ɛ and Reynolds stress) in predicting this flow field. The effects of computational domain size, grid resolution and different discretization schemes on the predictions are discussed. The existence of a recirculation flow region, a merging region and a combined region in the two parallel plane jet configuration has been predicted qualitatively by all three turbulence models. On the other hand, quantitative agreement between predictions and measurements varied by as much as 18 per cent for the merging length while the jet spread in the outer shear layer has been substantially under- predicted by all three models.

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