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Journal articles on the topic 'Jet exhaust plumes'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Salemann, V., and J. M. Williams. "A New Method of Modeling Underexpanded Exhaust Plumes for Wind Tunnel Aerodynamic Testing." Journal of Engineering for Gas Turbines and Power 111, no. 4 (October 1, 1989): 748–54. http://dx.doi.org/10.1115/1.3240322.

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A new method for modeling hot underexpanded exhaust plumes with cold model scale plumes in aerodynamic wind tunnel testing has been developed. The method is applicable to aeropropulsion testing where significant interaction between the exhaust and the free stream and aftbody may be present. The technique scales the model and nozzle external geometry, including the nozzle exit area, matches the model jet to free-stream dynamic pressure ratio to full-scale jet to free-stream dynamic pressure ratio, and matches the model thrust coefficient to full-scale thrust coefficient. The technique does not require scaling of the internal nozzle geometry. A generalized method of characteristic computer code was used to predict the plume shapes of a hot (γ = 1.2) half-scale nozzle of area ratio 3.2 and of a cold (γ = 1.4) model scale nozzle of area ratio 1.3, whose pressure ratio and area ratio were selected to satisfy the above criteria and other testing requirements. The plume shapes showed good agreement. Code validity was checked by comparing code results for cold air exhausting into a quiescent atmosphere to pilot surveys and shadowgraphs of model nozzle plumes taken in a static facility.

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2

Kärcher, B., and P. Fabian. "Dynamics of aircraft exhaust plumes in the jet-regime." Annales Geophysicae 12, no. 10/11 (August 31, 1994): 911–19. http://dx.doi.org/10.1007/s00585-994-0911-9.

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Abstract. A computational model describing the two-dimensional, turbulent mixing of a single jet of exhaust gas from aircraft engines with the ambient atmosphere is presented. The underlying assumptions and governing equations are examined and supplemented by a discussion of analytical solutions. As an application, the jet dynamics of a B747-400 aircraft engine in cruise and its dependence on key parameters is investigated in detail. The computer code for this dynamical model is computationally fast and can easily be coupled to complex chemical and microphysical models in order to perform comprehensive studies of atmospheric effects from aircraft exhaust emissions in the jet regime.

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3

Kärcher, B., and P. Fabian. "Dynamics of aircraft exhaust plumes in the jet-regime." Annales Geophysicae 12, no. 10 (1994): 911. http://dx.doi.org/10.1007/s005850050114.

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4

Dix, J., A. J. Saddington, K. Knowles, and M. A. Richardson. "Infra-red signature reduction study on a small-scale jet engine." Aeronautical Journal 109, no. 1092 (February 2005): 83–88. http://dx.doi.org/10.1017/s0001924000000580.

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Abstract This paper presents infra-red signature data for a small-scale, low pressure ratio turbojet engine typical of that used in unmanned air vehicle applications. The aim of the study was to test a number of different convergent nozzle designs concentrating on those with trailing edge modifications. The engine used in the tests has a single stage centrifugal compressor and radial inflow turbine and is designed to produce approximately 150N of thrust at 103,500rpm using liquid propane fuel. The test rig consisted of a calibrated thrust stand whilst the engine was controlled through an electronic engine control unit and laptop PC. The jet plume was visualised using an infra-red spectroradiometer which yielded qualitative data across the infra-red spectrum. Simultaneous measurements were also made of the engine thrust. A Pitot probe was used to take pressure readings across different sections of the exhaust flow. Analysis of the infrared signature of the engine exhaust plume and any thrust penalty yielded a performance comparison for each of the nozzles tested. Correlation of engine thrust with engine rpm showed that, within the accuracy of the measurements, there was no significant thrust penalty associated with the notched nozzles. Infra-red imagery of the plain and 60° notched nozzles indicated that the latter reduced the length of the hottest part of the exhaust plume by approximately 33%. The spectroradiometer data shows a significant reduction in spectral radiance for the CO2 wavelength of approximately 4·3µm when the notched nozzles are used. The 60° notched nozzle appeared to perform best in reducing the spectral radiance at this wavelength. Centreline total pressure measurements in the exhaust plume correlated well with the infra-red imagery in that a potential core length reduction of up to 30% could be achieved using the 60° notched nozzle. Total pressure contours recorded 20mm (0·43D) downstream of the nozzle exit plane suggest that the notched nozzles are promoting increased mixing through radial spreading of the jet possibly associated with increased streamwise vorticity (although the latter could not be confirmed). There were also signs that the jet plumes being investigated were swirling.

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5

Nasuti, F., R. Niccoli, and M. Onofri. "A Numerical Methodology to Predict Exhaust Plumes of Propulsion Nozzles." Journal of Fluids Engineering 120, no. 3 (September 1, 1998): 563–69. http://dx.doi.org/10.1115/1.2820699.

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A simple methodology to simulate the mixing layers that occur between nozzle exhaust jet and the external air is proposed. The method is based on a simplified model of the plume, that replaces the mixing layer with a contact discontinuity surface, thus avoiding the cumbersome calculation of the turbulent mixing of two flows with different chemical composition. The contact discontinuity is numerically treated by an advanced fitting technique, capable of tracking the discontinuity by points floating over the computational grid. The numerical method is discussed and its capability is demonstrated with validation tests, as well as with a discussion of some practical applications for underexpanded nozzle flows.

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6

Kärcher, B., and D. W. Fahey. "The role of sulfur emission in volatile particle formation in jet aircraft exhaust plumes." Geophysical Research Letters 24, no. 4 (February 15, 1997): 389–92. http://dx.doi.org/10.1029/97gl00119.

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7

Gao, R. S., B. Kärcher, E. R. Keim, and D. W. Fahey. "Constraining the heterogeneous loss of O3on soot particles with observations in jet engine exhaust plumes." Geophysical Research Letters 25, no. 17 (September 1, 1998): 3323–26. http://dx.doi.org/10.1029/98gl02505.

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8

Kärcher, B. "On the potential importance of sulfur-induced activation of soot particles in nascent jet aircraft exhaust plumes." Atmospheric Research 46, no. 3-4 (May 1998): 293–305. http://dx.doi.org/10.1016/s0169-8095(97)00070-7.

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9

Fisher, Edward M. D., Thomas Benoy, Gordon Humphries, David Wilson, M. Lengden, Walter Johnstone, Hugh McCann, et al. "A Custom, High-Channel Count Data Acquisition System for Chemical Species Tomography of Aero-Jet Engine Exhaust Plumes." IEEE Transactions on Instrumentation and Measurement 69, no. 2 (February 2020): 549–58. http://dx.doi.org/10.1109/tim.2019.2895932.

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10

Takegawa, Nobuyuki, Yoshiko Murashima, Akihiro Fushimi, Kentaro Misawa, Yuji Fujitani, Katsumi Saitoh, and Hiromu Sakurai. "Characteristics of sub-10 nm particle emissions from in-use commercial aircraft observed at Narita International Airport." Atmospheric Chemistry and Physics 21, no. 2 (January 27, 2021): 1085–104. http://dx.doi.org/10.5194/acp-21-1085-2021.

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Abstract. The characterization of ultrafine particle emissions from jet aircraft equipped with turbofan engines, which are commonly used in civil aviation, is an important issue in the assessment of the impacts of aviation on climate and human health. We conducted field observations of aerosols and carbon dioxide (CO2) near a runway at Narita International Airport, Japan, in February 2018. We used an ultrafine condensation particle counter (UCPC) and a condensation particle counter (CPC) with unheated and 350 ∘C heated operation modes to investigate the contributions of sub-10 nm size ranges to the total and the non-volatile particle number concentrations. The performance of the 350 ∘C heated mode was tested in the laboratory to verify the consistency with existing methods for non-volatile particle measurements. We also used a scanning mobility particle sizer with unheated and 350 ∘C heated modes and an engine exhaust particle sizer for the measurements of particle number size distributions. Spiked increases in the particle number concentrations and CO2 mixing ratios were observed to be associated with the directions of wind from the runway, which can be attributed to diluted aircraft exhaust plumes. We estimated the particle number emission indices (EIs) for discrete take-off plumes using the UCPC, CPC, and CO2 data. The median values of the total and the non-volatile particle number EIs for diameters larger than 2.5 nm as derived from the UCPC data were found to be 1.1×1017 and 5.7×1015 kg per fuel, respectively. More than half the particle number EIs were in the size range smaller than 10 nm for both the total and the non-volatile particles in most of the cases analyzed in this study. The significance of sub-10 nm size ranges for the total particles in the diluted plumes was qualitatively consistent with previous studies, but that for the non-volatile particles was unexpected. Possible factors affecting the similarities and differences compared with the previous findings are discussed.

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11

Kiendler, A., S. Aberle, and F. Arnold. "Positive ion chemistry in the exhaust plumes of an air craft jet engine and a burner: investigations with a quadrupole ion trap mass spectrometer." Atmospheric Environment 34, no. 28 (January 2000): 4787–93. http://dx.doi.org/10.1016/s1352-2310(00)00253-3.

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12

Chan, Tat Leung, Kun Zhou, and Jian Zhong Lin. "MODELING STUDY OF GAS-TO-NANOPARTICLE CONVERSION FROM A VEHICULAR EXHAUST JET PLUME(Jet and Plume)." Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2005 (2005): 405–11. http://dx.doi.org/10.1299/jsmeicjwsf.2005.405.

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13

Wang, Yi, Lei Cao, Yanqiu Huang, and Yingxue Cao. "Lateral ventilation performance for removal of pulsating buoyant jet under the influence of high-temperature plume." Indoor and Built Environment 29, no. 4 (November 8, 2019): 543–57. http://dx.doi.org/10.1177/1420326x19886639.

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Lateral exhaust systems have commonly been applied to capture polluted buoyant jets in many industrial processes, such as casting and metallurgy. Compared with the normal conditions of design manuals, the capture efficiency of a lateral exhaust hood (LEH) is often weakened by two factors in actual processes: the unsteady buoyant jet released from the operating surface, and the plume formed above a high-temperature workpiece placed between the LEH and the operating surface. In this study, through experiments and numerical simulations, a pulsatile phenomenon was found in the velocity and concentration distribution of the unsteady buoyant jet. Results show that the contaminate escape ratio is pulsatile; it rises with the instantaneous increase in the buoyant jet velocity and gradually decreases to a constant value. This study not only reveals the air distribution of pulsating buoyant jet but also analyses the effect of the pulsating buoyant jet and high-temperature plume on lateral ventilation system capture efficiency and provides a possible guidance for future design of new building ventilation technologies.

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14

NISHI, Akira. "Dispersion Process of Jet Engine Exhaust Plume : 2nd Report, Buoyant Jet." Bulletin of JSME 28, no. 244 (1985): 2360–64. http://dx.doi.org/10.1299/jsme1958.28.2360.

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15

Nelson, H. F., and E. O. Tucker. "Boron slurry-fueled jet engine exhaust plume infrared signatures." Journal of Spacecraft and Rockets 23, no. 5 (September 1986): 527–33. http://dx.doi.org/10.2514/3.25840.

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16

Beier, K., and F. Schreier. "Modeling of aircraft exhaust emissions and infrared spectra for remote measurement of nitrogen oxides." Annales Geophysicae 12, no. 10/11 (August 31, 1994): 920–43. http://dx.doi.org/10.1007/s00585-994-0920-8.

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Abstract. Infrared (IR) molecular spectroscopy is proposed to perform remote measurements of NOx concentrations in the exhaust plume and wake of aircraft. The computer model NIRATAM is applied to simulate the physical and chemical properties of the exhaust plume and to generate low resolution IR spectra and synthetical thermal images of the aircraft in its natural surroundings. High-resolution IR spectra of the plume, including atmospheric absorption and emission, are simulated using the molecular line-by-line radiation model FASCODE2. Simulated IR spectra of a Boeing 747-400 at cruising altitude for different axial and radial positions in the jet region of the exhaust plume are presented. A number of spectral lines of NO can be identified that can be discriminated from lines of other exhaust gases and the natural atmospheric background in the region around 5.2 µm. These lines can be used to determine NO concentration profiles in the plume. The possibility of measuring nitrogen dioxide NO2 is also discussed briefly, although measurements turn out to be substantially less likely than those of NO. This feasibility study compiles fundamental data for the optical and radiometric design of an airborne Fourier transform spectrometer and the preparation of in-flight measurements for monitoring of aircraft pollutants.

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17

Garnier, F., S. Brunet, and L. Jacquin. "Modelling exhaust plume mixing in the near field of an aircraft." Annales Geophysicae 15, no. 11 (November 30, 1997): 1468–77. http://dx.doi.org/10.1007/s00585-997-1468-1.

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Abstract. A simplified approach has been applied to analyse the mixing and entrainment processes of the engine exhaust through their interaction with the vortex wake of an aircraft. Our investigation is focused on the near field, extending from the exit nozzle until about 30 s after the wake is generated, in the vortex phase. This study was performed by using an integral model and a numerical simulation for two large civil aircraft: a two-engine Airbus 330 and a four-engine Boeing 747. The influence of the wing-tip vortices on the dilution ratio (defined as a tracer concentration) shown. The mixing process is also affected by the buoyancy effect, but only after the jet regime, when the trapping in the vortex core has occurred. In the early wake, the engine jet location (i.e. inboard or outboard engine jet) has an important influence on the mixing rate. The plume streamlines inside the vortices are subject to distortion and stretching, and the role of the descent of the vortices on the maximum tracer concentration is discussed. Qualitative comparison with contrail photograph shows similar features. Finally, tracer concentration of inboard engine centreline of B-747 are compared with other theoretical analyses and measured data.

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18

Ma, Song, Jianguo Tan, Xiankai Li, and Jiang Hao. "The effect analysis of an engine jet on an aircraft blast deflector." Transactions of the Institute of Measurement and Control 41, no. 4 (March 26, 2018): 990–1001. http://dx.doi.org/10.1177/0142331218755892.

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This paper establishes a novel mathematical model for computing the plume flow field of a carrier-based aircraft engine. Its objective is to study the impact of jet exhaust gases with high temperature, high speed and high pressure on the jet blast deflector. The working condition of the nozzle of a fully powered on engine is first determined. The flow field of the exhaust jet is then numerically simulated at different deflection angle using the three-dimensional Reynolds averaged Navier–Stokes equations and the standard [Formula: see text]-[Formula: see text] turbulence method. Moreover, infra-red temperature tests are further carried out to test the temperature field when the jet blast deflector is at the [Formula: see text] deflection angle. The comparison between the simulation results and the experimental results show that the proposed computation model can perfectly describe the system. There is only 8–10% variation between them. A good verification is achieved. Moreover, the experimental results show that the jet blast deflector plays an outstanding role in driving the high-temperature exhaust gases. It is found that [Formula: see text] may be the best deflection angle to protect the deck and the surrounding equipment effectively. These data results provide a valuable basis for the design and layout optimization of the jet blast deflector and deck.

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19

NISHI, Akira. "Dispersion process of jet engine exhaust plume. 2nd report Buoyant effect of heated jet." Transactions of the Japan Society of Mechanical Engineers Series B 51, no. 462 (1985): 716–20. http://dx.doi.org/10.1299/kikaib.51.716.

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20

Hromisin, Scott M., Russell W. Powers, and Leighton M. Myers. "Unsteady velocity measurements of model-scale supersonic exhaust jets in military-relevant configurations." International Journal of Aeroacoustics 17, no. 1-2 (February 24, 2018): 184–215. http://dx.doi.org/10.1177/1475472x17743634.

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Of the utmost importance is the need to better understand the high temperature, high velocity flow fields generated by military tactical aircraft during “run up” and take-off that gives rise to extremely hazardous conditions for personnel and equipment within the vicinity of the aircraft. The present study aims to fill the need for high frequency, two velocity component measurements throughout the flow fields produced by university-scale supersonic jets exhausting from nozzles in configurations relevant to practical, full-scale application. Specifically, this work focuses on studying the supersonic jets operating in two basic configurations: horizontal, free jets and jets impinging normal to a ground plane reminiscent of current short-takeoff and vertical landing aircraft. Experiments are conducted at nozzle operating conditions similar to those of full-scale aircraft. Both mean velocities and turbulence components are measured in both flow fields using a laser Doppler velocimeter. Axial components of the mean flow and turbulence are measured in the free jet. In the single impinging jet flow field two-component mean velocity and turbulence components are measured in the jet plume, impingement region, and outwash flow. Free jet velocity measurements show good consistency with 50% increase in jet Reynolds number. Turbulence intensities up to 15% of the mean jet exit velocity are observed at the nozzle exit plane. Laser Doppler measurements in the outwash of an impinging jet show turbulent fluctuations produce unsteady velocities well above the mean value. Two-component impinging jet unsteady velocity spectra show a distinct peak at the same frequency as the impingement tone observed in prior impinging jet acoustic field measurements.

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21

Hilton, M., A. H. Lettington, and C. W. Wilson. "Gas Turbine Exhaust Emissions Monitoring Using Nonintrusive Infrared Spectroscopy." Journal of Engineering for Gas Turbines and Power 120, no. 3 (July 1, 1998): 514–18. http://dx.doi.org/10.1115/1.2818175.

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Infrared (IR) spectra of the exhaust emissions from a static gas turbine engine have been studied using Fourier Transform (FT) spectroscopic techniques. Passive detection of the infrared emission from remote (range ∼ 3 m) hot exhaust gases was obtained nonintrusively using a high spectral resolution (0.25 cm−1) FTIR spectrometer. Remote gas temperatures were determined from their emission spectra using the total radiant flux method or by analysis of rotational line structure. The HITRAN database of atmospheric species was used to model the emission from gas mixtures at the relevant temperatures. The spatial distribution of molecular species across a section transverse to the exhaust plume ∼10 cm downstream of the jet pipe nozzle was studied using a tomographic reconstruction procedure. Spectra of the infrared emission from the plume were taken along a number of transverse lines of sight from the centerline of the engine outwards. A mathematical matrix inversion technique was applied to reconstruct the molecular concentrations of CO and CO2 in concentric regions about the centerline. Quantitative measurement of the molecular species concentrations determined nonintrusively were compared with results from conventional extractive sampling techniques.

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22

Castner, Raymond, Khairul Zaman, Amy Fagan, and Christopher Heath. "Wedge Shock and Nozzle Exhaust Plume Interaction in a Supersonic Jet Flow." Journal of Aircraft 54, no. 1 (January 2017): 125–34. http://dx.doi.org/10.2514/1.c033623.

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23

Paulec, Mason, Michael Marciniak, Kevin Gross, and Benjamin Akers. "Tomographic reconstruction of a jet engine exhaust plume using an infrared hyperspectral imager." Optical Engineering 57, no. 10 (October 16, 2018): 1. http://dx.doi.org/10.1117/1.oe.57.10.103103.

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24

Hagen, D. E., P. D. Whitefield, and H. Schlager. "Particulate emissions in the exhaust plume from commercial jet aircraft under cruise conditions." Journal of Geophysical Research: Atmospheres 101, no. D14 (August 1, 1996): 19551–57. http://dx.doi.org/10.1029/95jd03276.

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25

Hu, Jichao, Juntao Chang, and Wen Bao. "Ignition and Flame Stabilization of a Strut-Jet RBCC Combustor with Small Rocket Exhaust." Scientific World Journal 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/675498.

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A Rocket Based Combined Cycle combustor model is tested at a ground direct connected rig to investigate the flame holding characteristics with a small rocket exhaust using liquid kerosene. The total temperature and the Mach number of the vitiated air flow, at exit of the nozzle are 1505 K and 2.6, respectively. The rocket base is embedded in a fuel injecting strut and mounted in the center of the combustor. The wall of the combustor is flush, without any reward step or cavity, so the strut-jet is used to make sure of the flame stabilization of the second combustion. Mass flow rate of the kerosene and oxygen injected into the rocket is set to be a small value, below 10% of the total fuel when the equivalence ratio of the second combustion is 1. The experiment has generated two different kinds of rocket exhaust: fuel rich and pure oxygen. Experiment result has shown that, with a relative small total mass flow rate of the rocket, the fuel rich rocket plume is not suitable for ignition and flame stabilization, while an oxygen plume condition is suitable. Then the paper conducts a series of experiments to investigate the combustion characteristics under this oxygen pilot method and found that the flame stabilization characteristics are different at different combustion modes.

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26

Arnold, F., J. Curtius, B. Sierau, V. Bürger, R. Busen, and U. Schumann. "Detection of massive negative chemiions in the exhaust plume of a jet aircraft in flight." Geophysical Research Letters 26, no. 11 (June 1, 1999): 1577–80. http://dx.doi.org/10.1029/1999gl900304.

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27

Curtius, J., B. Sierau, F. Arnold, R. Baumann, R. Busen, P. Schulte, and U. Schumann. "First direct sulfuric acid detection in the exhaust plume of a jet aircraft in flight." Geophysical Research Letters 25, no. 6 (March 15, 1998): 923–26. http://dx.doi.org/10.1029/98gl00512.

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28

Xiao-lin, Sun, Wang Zhan-xue, Zhou Li, Shi Jing-wei, and Cheng Wen. "Internal flow and external jet characteristics of double serpentine nozzle with different aspect ratio." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 2 (November 2, 2017): 545–60. http://dx.doi.org/10.1177/0954410017737326.

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In order to increase the survivability of the fighter aircraft, the serpentine nozzle has been applied in series of stealth bombers and unmanned aerial vehicles due to its excellent potentiality of evidently suppressing the infrared radiation signatures and radar cross section emitted by engine exhausts. Among the geometric parameters of the serpentine nozzle, the aspect ratio (AR) at the nozzle exit is one of the most critical parameters for the nozzle design as the infrared suppression effect could be greatly enhanced with the increment of AR by strengthening the mixing between the exhaust plume and atmosphere; the aim of this paper is to study the influence of the AR on the flow characteristics of the double serpentine nozzle. The flow features of six double serpentine convergent nozzles, i.e. AR = 3, 5, 7, 9, 11, 15 respectively, were numerically simulated with the shear stress transport κ–ω turbulent model adopted, which had been validated by the experimental data. The characteristics of internal flow and external jet, and the aerodynamic performances of these six nozzles were compared. Results show that the Ma contours at the symmetric plane are different due to the distinct flow accelerations caused by the change of the curvature and the duct height for diverse AR, and the surface pressure and the shock wave features are different correspondingly. The lateral divergence and the lateral convergence characteristics of the nozzle configuration lead to opposite lateral flow under diverse AR, and the change of lateral width induced different lateral pressure gradient, then lead to various lateral vortex distributions. The length of potential core is the contribution of the comprehensive effects of geometry parameters, and it is decreased with the increase of AR due to the dominated effect of the increased mixing area; however, the declining rate is slowed down. The AR of 5 should be chosen for the best aerodynamic performance of the double serpentine nozzle under the qualifications to completely shield the high-temperature turbine.

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29

Lewellen, David C. "A Large-Eddy Simulation Study of Contrail Ice Number Formation." Journal of the Atmospheric Sciences 77, no. 7 (July 1, 2020): 2585–604. http://dx.doi.org/10.1175/jas-d-19-0322.1.

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AbstractIce crystal number is a critical ingredient in the potential climate impact of persistent contrails and contrail-induced cirrus. We perform an extensive set of large-eddy simulations (LES) of ice nucleation and growth within aircraft exhaust jets with an emphasis on assessing the importance of detailed plume mixing on the effective ice-number emission index (EIiceno) produced for different conditions. Parameter variations considered include ambient temperature, pressure, and humidity; initial aerosol origin (exhaust or ambient), number, and properties; and aircraft engine size. The LES are performed in a temporal representation with binned microphysics including the basics of activation of underlying aerosol, droplet growth, and freezing. We find that a box-model approach reproduces EIiceno from LES well for sufficiently low aerosol numbers or when crystal production is predominantly on ambient aerosol. For larger exhaust aerosol number the box model generally overestimates EIiceno and can underestimate the fraction from ultrafine aerosol. The effects of different parameters on EIiceno can largely be understood with simpler analytic models that are formulated in low and high aerosol-number limits. The simulations highlight the potential importance of “cold” contrails, ambient ultrafine aerosols, crystal loss due to competition between different-sized crystals, and limitations on reducing EIiceno. We find EIiceno insensitive to engine size for lower aerosol numbers, but decreasing with increasing engine size for higher aerosol numbers. Temporal versus spatial representations for jet LES are compared in an appendix.

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30

Raman, G., and A. B. Cain. "Innovative actuators for active flow and noise control." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 216, no. 6 (June 1, 2002): 303–24. http://dx.doi.org/10.1243/095441002321029044.

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Active flow control (AFC) has the potential to improve the efficiency of systems that involve both internal and external fluid flow. The primary driver in AFC is the expectation that the control will result in significant performance benefits at the system level with all trade-offs factored in. Successful application to aircraft systems can produce lighter, stealthier, agile aircraft with increased range, payload and a muffled acoustic signature. The design of an AFC system requires knowledge of flow phenomena and the selection of appropriate actuators, sensors and a control algorithm. The present overview focuses on actuators. Examples of flow and noise control presented here are restricted to open-loop systems. Various aspects of actuator utilization include actuator output characterization, exploiting resonances (plenum, structural or aeroacoustic) to enhance actuator amplitude and the different modes of actuation. A brief description of a high-bandwidth actuator is also provided, followed by a variety of application examples including edgetone suppression, cavity noise suppression, impingement noise suppression and jet mixing enhancement. The review concludes with a description of the successful application of AFC to the exhaust plume from an aircraft engine (JT8D).

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31

Wong, H. W., A. J. Beyersdorf, C. M. Heath, L. D. Ziemba, E. L. Winstead, K. L. Thornhill, K. M. Tacina, et al. "Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the formation of contrail ice particles in the jet regime." Atmospheric Chemistry and Physics Discussions 11, no. 9 (September 28, 2011): 26791–813. http://dx.doi.org/10.5194/acpd-11-26791-2011.

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Abstract. Contrails and contrail-induced cirrus clouds are identified as the most uncertain components in determining aviation impacts on global climate change. Parameters affecting contrail ice particle formation immediately after engine exit plane (<5 s in plume age) may be critical to ice particle properties used in large scale models predicting contrail radiative forcing. Despite this, detailed understanding of these parametric effects is still limited. In this paper, we present results from recent laboratory and modeling studies conducted to investigate the effects of water and soot emissions and ambient conditions on the near-field formation of contrail ice particles. The Particle Aerosol Laboratory (PAL) at the NASA Glenn Research Center and the Aerodyne microphysical parcel model for contrail ice particle formation were employed. Our studies show that exhaust water concentrations have a significant impact on contrail ice particle formation. When soot was introduced, ice particle formation was observed only when exhaust water concentration was above a critical level. When no soot or sulfuric acid was introduced, homogeneous ice particle formation was unfavorable. Soot particles were found to compete for water vapor condensation, and higher soot concentrations emitted into the chamber resulted in smaller ice particles being formed. Chamber conditions corresponding to higher altitude standard day conditions were found to favor ice particle formation as expected. The microphysical model captures experimental trends well, but discrepancies between the model and the experiments exist as the model predicts narrower ice particle size distributions and ice particle sizes nearly a factor of two larger than measured. These discrepancies are likely due to the lack of treatment of turbulent mixing in the model and particle loss and scatter during the experimental sampling process. Future measurement activities are planned to investigate other important parameters, such as soot surface properties and sulfuric acid concentrations, using the PAL and microphysical model.

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32

Hasan, R. G. M., J. J. McGuirk, D. D. Apsley, and M. A. Leschziner. "A turbulence model study of separated 3D jet/afterbody flow." Aeronautical Journal 108, no. 1079 (January 2004): 1–14. http://dx.doi.org/10.1017/s0001924000004942.

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Three-dimensional RANS calculations and comparisons with experimental data are presented for subsonic and transonic flow past a non-axisymmetric (rectangular) nozzle/afterbody typical of those found in fast-jet aircraft. The full details of the geometry have been modelled, and the flow domain includes the internal nozzle flow and the jet exhaust plume. The calculations relate to two free-stream Mach numbers of 0-6 and 0-94 and have been performed during the course of a collaborative research programme involving a number of UK universities and industrial organisations. The close interaction between partners contributed greatly to the elimination of computational inconsistencies and to rational decisions on common grids and boundary conditions, based on a range of preliminary computations. The turbulence models used in the study include linear and non-linear eddy-viscosity models. For the lower Mach number case, the flow remains attached and all of the turbulence models yield satisfactory pressure predictions. However, for the higher Mach number, the flow over the afterbody is massively separated, and the effect of turbulence model performance is pronounced. It is observed that non-linear eddy-viscosity modelling provides improved shock capturing and demonstrates significant turbulence anisotropy. Among the linear eddy-viscosity models, the SST model predicts the best surface pressure distributions. The standard k -ε model gives reasonable results, but returns a shock location which is too far downstream and displays a delayed recovery. The flow field inside the jet nozzle is not influenced by turbulence modelling, highlighting the essentially inviscid nature of the flow in this region. However, the resolution of internal shock cells for identical grids is found to be dependent on the solution algorithm -specifically, whether it solves for pressure or density as a main dependent variable. Density-based time-marching schemes are found to return a better resolution of shock reflection. The paper also highlights the urgent need for more detailed experimental data in this type of flow.

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Arnold, F., K. H. Wohlfrom, M. W. Klemm, J. Schneider, K. Gollinger, U. Schumann, and R. Busen. "First gaseous ion composition measurements in the exhaust plume of a jet aircraft in flight: Implications for gaseous sulfuric acid, aerosols, and chemiions." Geophysical Research Letters 25, no. 12 (June 15, 1998): 2137–40. http://dx.doi.org/10.1029/98gl01579.

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Chae, J. H., J. H. Lee, J. W. Lee, N. K. Ha, D. G. Kim, H. S. Jang, and R. S. Myong. "COMPUTATIONAL ANALYSIS OF EFFECTS OF THERMAL FLOW FIELD AND CHEMICAL COMPONENTS ON THE IR SIGNATURE IN THE EXHAUST PLUME OF A MICRO JET ENGINE." Journal of Computational Fluids Engineering 24, no. 3 (September 30, 2019): 101–11. http://dx.doi.org/10.6112/kscfe.2019.24.3.101.

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Wong, H. W., A. J. Beyersdorf, C. M. Heath, L. D. Ziemba, E. L. Winstead, K. L. Thornhill, K. M. Tacina, et al. "Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the properties of contrail ice particles in the jet regime." Atmospheric Chemistry and Physics 13, no. 19 (October 11, 2013): 10049–60. http://dx.doi.org/10.5194/acp-13-10049-2013.

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Abstract. Contrails and contrail-induced cirrus clouds are identified as the most uncertain components in determining aviation impacts on global climate change. Parameters affecting contrail ice particle formation immediately after the engine exit plane (< 5 s in plume age) may be critical to ice particle properties used in large-scale models predicting contrail radiative forcing. Despite this, detailed understanding of these parametric effects is still limited. In this paper, we present results from recent laboratory and modeling studies conducted to investigate the effects of water and soot emissions and ambient conditions on near-field formation of contrail ice particles and ice particle properties. The Particle Aerosol Laboratory (PAL) at the NASA Glenn Research Center and the Aerodyne microphysical parcel model for contrail ice particle formation were employed. Our studies show that exhaust water concentration has a significant impact on contrail ice particle formation and properties. When soot particles were introduced, ice particle formation was observed only when exhaust water concentration was above a critical level. When no soot or sulfuric acid was introduced, no ice particle formation was observed, suggesting that ice particle formation from homogeneous nucleation followed by homogeneous freezing of liquid water was unfavorable. Soot particles were found to compete for water vapor condensation, and higher soot concentrations emitted into the chamber resulted in smaller ice particles being formed. Chamber conditions corresponding to higher cruising altitudes were found to favor ice particle formation. The microphysical model captures trends of particle extinction measurements well, but discrepancies between the model and the optical particle counter measurements exist as the model predicts narrower ice particle size distributions and ice particle sizes nearly a factor of two larger than measured. These discrepancies are likely due to particle loss and scatter during the experimental sampling process and the lack of treatment of turbulent mixing in the model. Our combined experimental and modeling work demonstrates that formation of contrail ice particles can be reproduced in the NASA PAL facility, and the parametric understanding of the ice particle properties from the model and experiments can potentially be used in large-scale models to provide better estimates of the impact of aviation contrails on climate change.

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"CFD Prediction of the Trajectory of Hot Exhaust from the Funnel of a Naval Ship in the Presence of Ship Superstructure." International Journal of Maritime Engineering 156, A1 (March 1, 2014). http://dx.doi.org/10.3940/rina.ijme.2014.a1.269.

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The superstructure of a modern naval ship is fitted with multitude of sensors for electronic surveillance, weapon discharge, navigation, communication and varieties of deck handling equipment. Locating these electronic equipment/sensors and its integration on board is of paramount importance to achieve optimal operational performance of the naval vessel. Among the many problems in locating these sensors (like stability, EMC EMI etc.,), the presence of entrapped hot gases from the ship exhaust affects the functioning of these electronics. Hence the prediction of temperature profile and trajectories of the ship exhaust plume from the funnel around the superstructure during the design stage is a mandatory requirement for positioning the sensors on superstructure. This trajectory prediction is not amenable to theoretical analysis or empirical calculation procedures in the modern warship superstructure. Experimental and CFD studies conducted on ship superstructure are the only reliable tools that are available to estimate temperature field as well as to study the exhaust smoke superstructure interaction on ships. This paper presents the CFD simulation of the published results for two cases, namely hot jet in a cross flow and hot exhaust with a cross flow on a generic frigate. Simulations have been made using k-ɛ turbulence model with different values of turbulent Schmidt number. It has been observed that temperature field is predicted with reasonable accuracy with turbulent Schmidt number of 0.2.

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Yin, Z. Q., J. Z. Lin, K. Zhou, and T. L. Chan. "Numerical Simulation of the Formation of Pollutant Nanoparticles in the Exhaust Twin-jet Plume of A Moving Car." International Journal of Nonlinear Sciences and Numerical Simulation 8, no. 4 (January 2007). http://dx.doi.org/10.1515/ijnsns.2007.8.4.535.

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Curtius, J. "Sulfuric acid measurements in the exhaust plume of a jet aircraft in flight: Implications for the sulfuric acid formation efficiency." Geophysical Research Letters 29, no. 7 (2002). http://dx.doi.org/10.1029/2001gl013813.

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Cantin, Sébastien, Mohamed Chouak, François Morency, and François Garnier. "Eulerian–Lagrangian CFD-microphysics modeling of a near-field contrail from a realistic turbofan." International Journal of Engine Research, February 19, 2021, 146808742199396. http://dx.doi.org/10.1177/1468087421993961.

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Aircraft contrails contribute to climate change through global radiative forcing. As part of the general effort aimed at developing reliable decision-making tools, this paper demonstrates the feasibility of implementing a Lagrangian ice microphysical module in a commercial CFD code to characterize the early development of near-field contrails. While engine jets are highly parameterized in most existing models in a way that neglects the nozzle exit-related aspects, our model accounts for the geometric complexity of modern turbofan exhausts. The modeling strategy is based on three-dimensional URANS simulations of an aircraft nozzle exit involving a bypass and a core jet (Eulerian gas phase). Solid soot and ice particles (dispersed phase) are individually tracked using a Lagrangian approach. The implemented microphysical module accounts for the main process of water-vapor condensation on pre-activated soot particles known as heterogeneous condensation. The predictive capabilities of the proposed model are demonstrated through a comprehensive validation set based on the jet-flow dynamics and turbulence statistics in the case of compressible, turbulent coaxial jets. Simulations of contrail formation from a realistic nozzle-exit geometry of the CFM56-3 engine (short-cowl nozzle delivering a dual stream jet with a bypass rate of 5.3) were also carried out in typical cruise flight conditions ensuring contrail formation. The model provides reliable predictions in terms of the plume dilution and ice-particle properties as compared to available in-flight and numerical data. Such a model can then be used to characterize the impact of nozzle-exit parameters on the optical and microphysical properties of near-field contrails.

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DeBonis, James R. "RANS Analyses of Turbofan Nozzles With Internal Wedge Deflectors for Noise Reduction." Journal of Fluids Engineering 131, no. 4 (March 9, 2009). http://dx.doi.org/10.1115/1.3089536.

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Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of a promising concept for reducing the noise at take-off of dual-stream turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) a portion of the fan flow below the core flow, thickening and lengthening this layer between the high-velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds averaged Navier–Stokes (RANS) code, was used to analyze the flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept.

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Herndon, J. Marvin, and Mark Whiteside. "Geophysical Consequences of Tropospheric Particulate Heating: Further Evidence that Anthropogenic Global Warming is Principally Caused by Particulate Pollution." Journal of Geography, Environment and Earth Science International, August 19, 2019, 1–23. http://dx.doi.org/10.9734/jgeesi/2019/v22i430157.

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The climate science community and the United Nations’ Intergovernmental Panel on Climate Change have misinformed world governments by failing to acknowledge tropospheric particulate geoengineering that has been ongoing with ever-increasing duration and intensity for decades, and by treating global warming solely as a radiation-balance issue, which has resulted in a seriously incomplete understanding of the fundamental factors that affect Earth’s surface temperature. Here we review the consequences of tropospheric particulate heating by absorption of short- and long-wave solar radiation and long-wave radiation from Earth’s surface. Generally, black carbon absorbs light over the entire solar spectrum; brown carbon absorbs near-UV wavelengths and, to a lesser extent, visible light; iron oxides are good absorbers, the most efficient being magnetite. Pyrogenic coal fly ash, both from coal burning and from tropospheric jet-spraying geoengineering (for military purposes and/or climate engineering), contains carbon and iron oxides, hematite and magnetite. The recently published climate-science paradigm shift discloses that the main cause of global warming is not carbon dioxide heat retention, but particulate pollution that absorbs radiation, heats the troposphere, and reduces the efficiency of atmospheric-convective heat removal from Earth’s surface. In addition to the World War II data, three other independent lines of supporting evidence are reviewed: (1) Passage overhead of the Mt. St. Helens volcanic plume; (2) Radiosonde and aethalometer investigations of Talukdar et al.; and, (3) convection suppression over the tropical North Atlantic caused by the Saharan-blown dust. The risks associated with the placement of aerosol particulates into the stratosphere, whether lofted naturally, inadvertently, or deliberately as proposed for solar radiation management, poses grave risks, including the destruction of atmospheric ozone. To solve global warming humanity must: (1) Abruptly halt tropospheric particulate geoengineering; (2) Trap particulate emissions from coal-fired industrial furnaces (especially in India and China) and from vehicle exhaust; and, (3) Reduce particulate-forming fuel additives.

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