Experimental investigation on mixing characteristics of high speed co-flow jets by using tabbed chevron nozzle

Abstract The present study investigates the effect of chevron with tab (Tabbed chevron) fixed at the exit of the co-flowing primary nozzle on the mixing characteristics in subsonic and sonic jets. The experiment was conducted for the jet Mach number 0.6 and 0.8. The centerline Mach number decay was calculated for all these jet Mach numbers for the co-flow baseline nozzle, nozzle with chevrons and tabbed chevron (primary flow) nozzle respectively. It was found that tabbed chevron was effective in reducing the potential core length by 88.23% as compared to the chevron nozzle with baseline nozzle. The radial profile also shows that the mixing enhancement by tabbed chevron is better than chevron nozzle.

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Active control of high-speed and high-Reynolds-number jets using plasma actuators

Journal of Fluid Mechanics ◽

10.1017/s0022112007004867 ◽

2007 ◽

Vol 578 ◽

pp. 305-330 ◽

Cited By ~ 271

Author(s):

M. SAMIMY ◽

J.-H. KIM ◽

J. KASTNER ◽

I. ADAMOVICH ◽

Y. UTKIN

Keyword(s):

Reynolds Number ◽

Nozzle Exit ◽

High Speed ◽

Low Reynolds Number ◽

Plasma Actuators ◽

Mixing Enhancement ◽

Azimuthal Mode ◽

Potential Core ◽

Low Speed ◽

Low Reynolds

Localized arc filament plasma actuators are used to control an axisymmetric Mach 1.3 ideally expanded jet of 2.54 cm exit diameter and a Reynolds number based on the nozzle exit diameter of about 1.1×106. Measurements of growth and decay of perturbations seeded in the flow by the actuators, laser-based planar flow visualizations, and particle imaging velocimetry measurements are used to evaluate the effects of control. Eight actuators distributed azimuthally inside the nozzle, approximately 1 mm upstream of the nozzle exit, are used to force various azimuthal modes over a large frequency range (StDF of 0.13 to 1.3). The jet responded to the forcing over the entire range of frequencies, but the response was optimum (in terms of the development of large coherent structures and mixing enhancement) around the jet preferred Strouhal number of 0.33 (f = 5 kHz), in good agreement with the results in the literature for low-speed and low-Reynolds-number jets. The jet (with a thin boundary layer, D/θ ∼ 250) also responded to forcing with various azimuthal modes (m = 0 to 3 and m = ±1, ±2, ±4), again in agreement with instability analysis and experimental results in the literature for low-speed and low-Reynolds-number jets. Forcing the jet with the azimuthal mode m = ±1 at the jet preferred-mode frequency provided the maximum mixing enhancement, with a significant reduction in the jet potential core length and a significant increase in the jet centreline velocity decay rate beyond the end of the potential core.

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On cumulative nonlinear acoustic waveform distortions from high-speed jets

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.228 ◽

2014 ◽

Vol 749 ◽

pp. 331-366 ◽

Cited By ~ 35

Author(s):

W. J. Baars ◽

C. E. Tinney ◽

M. S. Wochner ◽

M. F. Hamilton

Keyword(s):

Mach Number ◽

Acoustic Waves ◽

High Speed ◽

Scaling Laws ◽

Nonlinear Distortion ◽

Practical Interest ◽

Laboratory Scale ◽

Potential Core ◽

Nonlinear Distortions ◽

Gaussian Source

AbstractA model is proposed for predicting the presence of cumulative nonlinear distortions in the acoustic waveforms produced by high-speed jet flows. The model relies on the conventional definition of the acoustic shock formation distance and employs an effective Gol’dberg number$\Lambda $for diverging acoustic waves. The latter properly accounts for spherical spreading, whereas the classical Gol’dberg number$\Gamma $is restricted to plane wave applications. Scaling laws are then derived to account for the effects imposed by jet exit conditions of practical interest and includes Mach number, temperature ratio, Strouhal number and an absolute observer distance relative to a broadband Gaussian source. Surveys of the acoustic pressure produced by a laboratory-scale, shock-free and unheated Mach 3 jet are used to support findings of the model. Acoustic waveforms are acquired on a two-dimensional grid extending out to 145 nozzle diameters from the jet exit plane. Various statistical metrics are employed to examine the degree of local and cumulative nonlinearity in the measured waveforms and their temporal derivatives. This includes a wave steepening factor (WSF), skewness, kurtosis and the normalized quadrature spectral density. The analysed data are shown to collapse reasonably well along rays emanating from the post-potential-core region of the jet. An application of the generalized Burgers equation is used to demonstrate the effect of cumulative nonlinear distortion on an arbitrary acoustic waveform produced by a high-convective-Mach-number supersonic jet. It is advocated that cumulative nonlinear distortion effects during far-field sound propagation are too subtle in this range-restricted environment and over the region covered, which may be true for other laboratory-scale jet noise facilities.

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Effect of Strut Geometry in Supersonic Mixing

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.f1529.089620 ◽

2020 ◽

Vol 9 (6) ◽

pp. 386-389

Keyword(s):

Experimental Study ◽

Mach Number ◽

Residence Time ◽

High Speed ◽

Free Stream ◽

Mixing Enhancement ◽

Supersonic Mixing ◽

Mixing Chamber ◽

Mixing Method ◽

Selection Of

Effective mixing in a short mixing chamber is a major challenge in supersonic air breathing engines, especially the mixing between two high speed co-axial streams. The residence time is a major factor to get the two streams properly mixed. The selection of mixing method is crucial in the supersonic conditions. An experimental study has been performed on the supersonic mixing of air from strut injectors of various combinations in their trailing ramp angles with a free stream air of Mach number 2. Two different configurations of geometries, a plain geometry and a lobed geometry considered and further two different combinations, slot and hole injections, are taken for the study in each geometry. Among different combinations, it is found that a better mixing enhancement is achieved for the 9o lobed geometry struts.

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High-speed turbulent gas jets: an LES investigation of Mach and Reynolds number effects on the velocity decay and spreading rate

Flow Turbulence and Combustion ◽

10.1007/s10494-021-00242-5 ◽

2021 ◽

Author(s):

Francesco Bonelli ◽

Annarita Viggiano ◽

Vinicio Magi

Keyword(s):

Mach Number ◽

High Speed ◽

Stokes Equations ◽

Fluid Dynamic ◽

Spreading Rate ◽

Navier Stokes ◽

Potential Core ◽

Jet Mixing ◽

Gas Jets ◽

Velocity Decay

AbstractThe aim of this work is the investigation of Mach and Reynolds numbers effects on the behaviour of turbulent gas jets in order to gain new insights into the fluid dynamic process of turbulent jet mixing and spreading. An in-house solver (Flow-Large Eddy and Direct Simulation, FLEDS) of the Favre-filtered Navier Stokes equations has been used. Compressibility has been analyzed by considering gas jets with Mach number equal to 0.8, 1.4, 2.0 and 2.6, and Re equal to 10,000. As concerns the influence of Re on gas jets, four cases have been investigated, i.e. $$\mathrm{Re} = 2500$$ Re = 2500 , 5000, 10,000 and 20,000, with Mach number equal to 1.4. The results show that, in accordance with previous experimental and numerical studies, the potential core length increases with Mach number. As regards the velocity decay and the spreading rate downstream of the potential core, compressibility effects are not relevant except for the jet with Mach number of 2.6. The normalized turbulent kinetic energy along the centerline as a function of the normalized streamwise distance shows a similar peak at the end of the potential core for all jets, except for the case with Mach number of 2.6. By increasing Re, the length of the potential core decreases up to the same value for all Re higher than 10,000. In the region downstream of the potential core, the velocity decay decreases as Re number increases from 10,000 to 20,000, whereas, for lower values of Re, the influence is almost negligible.

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Experimental investigation of the protective effect of wind barriers on high-speed railway bridge in inland strong wind area

Advances in Structural Engineering ◽

10.1177/1369433219862939 ◽

2019 ◽

Vol 22 (15) ◽

pp. 3306-3318

Author(s):

Wanmin Ren ◽

Qingsong Duan ◽

Cunming Ma ◽

Haili Liao ◽

Qiusheng Li

Keyword(s):

Experimental Investigation ◽

Protective Effect ◽

High Speed ◽

Aerodynamic Characteristics ◽

Strong Wind ◽

Railway Bridge ◽

Box Girder ◽

High Speed Railway ◽

Wind Barrier ◽

Better Than

This study aims to investigate the wind protective effect of wind barriers on the Lanzhou–Xinjiang high-speed railway using wind tunnel tests. Wind barriers with different heights and porosities were analyzed. Two girders, that is, a box-girder and a trough-girder, each with 1:30 and 1:8 scales were experimentally investigated. The results suggest that the protective effect of the wind barrier with a height of 4 m and porosity of 20% is better than the others. The influence of wind barriers on the aerodynamic characteristics of train vehicles and girders must be analyzed simultaneously. The aerostatic force coefficients of trains are approximately the same at different scales, and the Reynolds number effect could be neglected.

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Investigation of mixing characteristics of coflow rectangular nozzle of aspect ratio 2 and 3

Aircraft Engineering and Aerospace Technology ◽

10.1108/aeat-04-2021-0097 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Vignesh Kumar Murugesan ◽

Aravindh Kumar Suseela Moorthi ◽

Ganapathy Subramanian L. Ramachandran

Keyword(s):

Aspect Ratio ◽

High Speed ◽

Exhaust System ◽

Commercial Aircraft ◽

Potential Core ◽

Sonic Nozzle ◽

Content Type ◽

Rectangular Nozzle ◽

Nozzle Pressure ◽

Mixing Characteristics

Purpose The purpose of this study is to understand experimentally the mixing characteristics of a two-stream exhaust system with a supersonic Mach 1.5 primary jet that exits the rectangular C-D nozzle surrounded by a sonic secondary jet from a convergent rectangular nozzle by varying the aspect ratio (AR = 2 and 3) similar to those that can be available for future high-speed commercial aircraft. Design/methodology/approach This paper focuses on the experimental results of effects of AR at various expansion levels of jets issued/delivered from a central rectangular convergent-divergent nozzle of AR 2 and 3 surrounded by a coflow from a convergent rectangular sonic nozzle. The lip thickness of the primary nozzle is 2.2 mm. various nozzle pressure ratios (NPRs) ranging from 2, 3, 3.69 and 4 were chosen for pressure measurements. Findings For all the NPRs, AR 3 had a shorter core than AR 2. Also, AR 3 was found to decay faster in the transition and fully developed zones. The lateral plots show that the AR has an influence on the jet spread. Originality/value The structure of waves existing in the potential core of the rectangular coflow jet along with the major and minor axis planes was visualized by the shadowgraph technique.

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Experimental Investigation of Spray Dynamics Under Jet Engine Augmentor-Like Conditions

Volume 1: Combustion and Fuels, Education ◽

10.1115/gt2006-91112 ◽

2006 ◽

Author(s):

Javier N. Johnson ◽

Eugene Lubarsky ◽

Ben T. Zinn

Keyword(s):

Experimental Investigation ◽

Mach Number ◽

Atmospheric Pressure ◽

High Speed ◽

Cross Flow ◽

Short Exposure ◽

Jet Engine ◽

Breakup Mechanism ◽

Jet Breakup ◽

Fuel Jet

This paper describes an experimental investigation of fuel spray jet breakup mechanisms when it is injected across the high temperature air flow in low and high pressure jet engine augmentor-like conditions. Phase Doppler particle analyzer data and short exposure pulsed shadow graph images were taken of fuel jet injected into an air cross flow with liquid to air momentum ratios ranging from 5 to 180. Measured droplet diameters taken at atmospheric pressure and a flow Mach number of ∼0.15 show a progressive breakup of the droplets, gradually decreasing in size from 250μm to 150μm and finally to 25 μm as the spray moves downstream. The progressive breakup of droplets follows the classical Rayleigh-Helmholtz breakup mechanism. At higher pressure and Mach number tests, the fuel jet undergoes a different breakup process; i.e., the fuel jet breaks up instantaneously into a monodispurse spray of smaller droplets near the injector. High speed images of this process suggest that an aerodynamic breakup mechanism dominates this atomization process near the injector. In summary, the results of this study show the fuel jet breakup mechanism in augmentors varies significantly over the flight envelope.

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