| 1. |
- Cuppoletti, Daniel, et al.
(author)
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Analysis of Supersonic Jet Thrust with Fluidic Injection
- 2014
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In: 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014; National Harbor, MD; United States; 13 January 2014 through 17 January 2014. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624102561
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Conference paper (peer-reviewed)abstract
- Considerable focus on noise abatement for aircraft has spawned various noise control devices, passive and active. Aircraft and propulsion system design now has the additional criteria of acoustic performance to consider among many other criteria in advanced flight vehicle design. It is essential to consider the effect that noise control methods have on the performance of the propulsion device and overall effect on system performance. Thrust calculated from measurements and LES are compared for a Md = 1.56 jet at various operating conditions for validation. Experimental measurements on the baseline supersonic jet are used to validate computational results for the pressure and momentum thrust components. Thrust for various fluidic injection configurations are evaluated using computational results from the highly three dimensional flowfield. Analysis and discussion of requirements for fluidic injection air are provided to develop a complete system approach to aid design of fluidic injection systems. Fluidic injection decreases momentum thrust by creating axial velocity deficits in the region of injection. Pressure thrust is increased from local pressure rise from the injectors and area control at the nozzle exit. Fluidic injection increases total thrust as the pressure thrust gains are greater than the momentum thrust deficits. Specific thrust is reduced slightly with 6 injectors being a more efficient use of the injection air with greater noise reduction.
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| 2. |
- Cuppoletti, Daniel, et al.
(author)
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Elimination of shock associated noise in supersonic jets by destructive wave interference
- 2018
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In: AIAA Aerospace Sciences Meeting, 2018. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Conference paper (peer-reviewed)abstract
- A novel application of fluidic injection was developed to investigate and understand the effects of discrete fluidic injection internal to the jet nozzle. Various injection locations, angles, and conditions were studied resulting in unique acoustic behavior and flow field modifications. For most conditions the acoustics are relatively unaffected or increased, but for very specific conditions noise was drastically decreased. For optimized conditions the shock noise was completely eliminated and in other cases a jet instability was generated that significantly decreased high frequency noise. Measurements of the velocity field indicated that shock interaction due to shocks from the injection jet interact with the primary jet shocks, and significantly reduce the shock strength, attributing massive shock noise reduction. Validation of the experimental results was achieved with LES, which provided additional insight into the shock suppression due to resolution of the flowfield internal to the nozzle. Optimal injection parameters resulted in reduction of OASPL of -7 dB at the upstream and downstream angles simultaneously through a combination of shock disruption and streamwise vorticity introduction. A new mechanism of supersonic jet noise reduction, destructive interference of the shock structure in the jet is reported.
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| 3. |
- Cuppoletti, Daniel, et al.
(author)
-
Elimination of Shock-Associated Noise in Supersonic Jets by Destructive Wave Interference
- 2019
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In: AIAA Journal. - 1533-385X .- 0001-1452. ; 57:2, s. 720-734
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Journal article (peer-reviewed)abstract
- A novel application of fluidic injection was developed to investigate and understand the effects of discrete fluidic injection internal to the jet nozzle. Various injection locations, angles, and conditions were studied, resulting in unique acoustic behavior and flowfield modifications. For most conditions, the acoustics are relatively unaffected or increased, but for very specific conditions, noise was drastically decreased. For optimized conditions, the shock noise was completely eliminated, and in other cases, a jet instability was generated that significantly decreased high-frequency noise. Measurements of the velocity field indicated that shock interaction, due to shocks from the injection jets, interacts with the primary jet shocks and significantly reduces the shock strength, attributing massive shock noise reduction. Validation of the experimental results was achieved with large-eddy simulation, which provided additional insight into the shock suppression due to resolution of the flowfield internal to the nozzle. Optimal injection parameters resulted in reduction of overall sound pressure level of -7 d B at the upstream and downstream angles simultaneously through a combination of shock disruption and streamwise vorticity introduction. A new mechanism of supersonic jet noise reduction and destructive interference of the shock structure in the jet is reported.
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| 4. |
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| 5. |
- Cuppoletti, Daniel, et al.
(author)
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The Role of Nozzle Contour on Supersonic Jet Thrust and Acoustics
- 2014
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In: AIAA Journal. - : American Institute of Aeronautics and Astronautics (AIAA). - 1533-385X .- 0001-1452. ; 52:11, s. 2594-2614
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Journal article (peer-reviewed)abstract
- This work is an experimental and computational investigation of acoustics and performance of a biconical and splined supersonic nozzle to identify the dependencies of noise components on the nozzle design. The convergent section and throat of a biconical supersonic nozzle were optimized with a Reynolds-averaged Navier-Stokes solver to optimize thrust and minimize internal losses. Far-field acoustics and the jet flowfield were measured and studied using large-eddy simulations at design, overexpanded, and underexpanded conditions. The biconical and splined nozzles are designed to be thrust matched at fully expanded conditions. The convergent section and throat contour do not significantly affect the turbulent mixing noise or shock-associated noise at most conditions. Analysis of the jet flowfield shows differences in shock structure, although the "global" shock strength remains relatively unchanged. A comparison of measurements and computations of mean velocity and turbulence shows minor differences in the shear-layer region and near strong shocks. Momentum thrust and pressure thrust were measured and compared with computational results. The contoured throat nozzle provides equivalent thrust with a 4% lower nozzle pressure ratio at the design condition with no acoustic penalty. At equivalent nozzle pressure ratios, the contoured nozzle provides 10% higher thrust with no increase in mixing noise or shock noise.
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| 6. |
- Daniel, Cuppoletti, et al.
(author)
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Nozzle Throat Optimization on Acoustics and Performance of a Supersonic Jet
- 2012
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In: 18th AIAA/CEAS Aeroacoustics Conference (33rd AIAA Aeroacoustics Conference). - Reston, Virigina : American Institute of Aeronautics and Astronautics.
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Conference paper (peer-reviewed)abstract
- Nozzles used in supersonic flight applications have flow contours that cause the flow to differ from isentropic nozzle flow, resulting in less than ideal nozzle performance. The impact of nozzle contour on performance is well quantified, however it is less clear how the nozzle contour affects supersonic jet noise. This work investigates differences in noise characteristics of a sharp throat and contoured throat nozzle to identify the dependencies of supersonic noise components on the nozzle design. The nozzles are designed to be thrust matched at fully expanded conditions. The throat contour does not significantly affect the acoustics at fully expanded conditions, although the nozzle efficiency is increased for the contoured throat nozzle. Contouring the throat causes the nozzle to have screech instabilities over a broader range of operating conditions when imperfectly expanded. A detailed PIV and LES investigation was used to explain the acoustics behavior at all conditions. Reducing the throat shock strength increased the nozzle exit shock strength and periodicity, subsequently increasing the susceptibility to screech. Nozzle performance is increased at all operating conditions with the contoured throat nozzle.
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| 7. |
- Gustafsson, Bernhard, 1971, et al.
(author)
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Nozzle throat optimization for supersonic jet noise reduction
- 2012
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In: 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition 2012. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
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Conference paper (peer-reviewed)abstract
- Noise from engines that operate at supersonic conditions, especially high performance military aircraft, often utilize a converging-diverging nozzle with variable area control. This design usually includes a sharp nozzle throat which creates internal shock formation. Turbulent structure interaction with these shocks results in additional noise components other than turbulent mixing noise to be introduced to the jet noise spectrum. The present study investigates how weakening the internal shocks affects the flow and acoustics of a Mach 1.6 jet. RANS simulations were used to minimize internal shock formation and optimize the flow contours of the converging portion and throat of a C-D nozzle. A response surface methodology was used to evaluate 3000 possible designs using the RANS results as model inputs. An experimental investigation was conducted with a splined nozzle design that is virtually free of internal shocks. The flow field was measured using PIV for comparison with RANS and LES. Mean velocity and turbulence was captured well by the computations for the sharp throat and splined nozzles. Although the throat shocks were nearly eliminated, the overall shock strength was relatively unchanged. Far-field acoustic results showed little difference at thrust matched conditions since the overall shock strength was unchanged. The nozzle performance is greatly improved through throat optimization, providing equivalent thrust with 4% less pressure with no acoustic penalty.
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| 8. |
- Hafsteinsson, Haukur, 1984, et al.
(author)
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Active Suppression of Supersonic Jet Noise Using Pulsating Micro-Jets
- 2012
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In: 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Nashville, 9-12 January 2012. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
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Conference paper (peer-reviewed)abstract
- Noise suppression devices on military jet engines are motivated by the need to reduce community noise aswell as the acoustic load on airfield personnel during peacetime operation. They may also reduce problemswith sonic fatigue on the aircraft. Micro-jets have previously been shown as a promising tool for active noisesuppression. In the work presented here, compressible LES simulations have been done for slightly overexpandedconical C-D nozzle with a Mach number of 1.58 at NPR = 4.0 and a free stream flow Mach numberof 0.1. Two microjet configurations have been simulated. One with steady-state injection and an other withpulsating trailing-edge injection having a maximum mass flow-rate of mi/mj = 1.6%. The acoustic field isexpanded to the far field using the Kirchhoff integral method. The effect of injection frequency and pulsationcharacteristics on the flow-field and the radiated sound is investigated. Comparison is made between the LESand simulations and experiments for the steady-state and no injection cases and shows excellent agreement forthe screech tone frequency and the predictided OASPL is within 2 dB deviation from the measurements. Thepulsating injection cases investigated show that the frequency spectrum and the noise levels are sensitive to theinjection frequency as well as pulsation characteristics. It is shown that steady-state injection and pulsating injectionof equal max mass flow result in comparable reduction in terms of OASPL. The latter, however, comeswith the penalty of increased noise for the upstream observers.
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| 9. |
- Hafsteinsson, Haukur, 1984, et al.
(author)
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Near-field and far-field spectral analyzis of supersonic jet with and without fluidic injection
- 2014
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In: 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014; National Harbor, MD; United States; 13 January 2014 through 17 January 2014. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624102561
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Conference paper (peer-reviewed)abstract
- In the presented study the time-dependent flow features of a supersonic jet with and without steady microjet injection are investigated. The flow field is sampled at various axial and radial locations in the supersonic region and its near surroundings. The jet is emitted from a sharp-throat converging diverging nozzle operated at a nozzle pressure ratio (NPR) of 4.0, which gives a jet exitMach number of M = 1.56 and a Reynolds number of Re = 2.46×106 based on the jet exit diameter. Large Eddy Simulation (LES) is used to obtain the fully three dimensional instantenous turbulent flow field and the Kirchhoff surface integral method is applied to obtain the far-field radiated noise. Both the near-field flow dynamics and the far-field noise obtained from the LES are in good agreement with experimental data. The noise components in the far-field noise are identified and compared with the spectra obtained from the probe-locations within the jet. The effect of micro-jet injection on the spectral characteristics within the jet and the far-field noise is analyzed. The screech tone appearing in the far-field noise is clearly established also in the jet-plume. Two point cross-correlations within and outside the supersonic region of the jet-plume revealed two types of moving phenomenon. These where found to be turbulent structures and acoustic waves. The odd thing at first sight was that the acoustic waves appeared to be traveling upstream within the supersonic region, which sounds contradictory. However, it was showed that the acoustic wave was traveling in the form of a helical mode which allows the phase velocity of the pressure wave to be higher than the flow velocity, even at supersonic flow speeds. The fluidic injection was shown to disrupt and weaken the helical pattern which resulted in a lower far-field screech tone noise. Upon sufficient dissipation of the injection, a few nozzle diameters downstream of the nozzle exit, the helical pattern picks up strength again. However, the feed-back loop mechanism associated with the screech tone is still disabled.
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| 10. |
- Hafsteinsson, Haukur, 1984, et al.
(author)
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Noise Control of Supersonic Jet with Steady and Flapping Fluidic Injection
- 2015
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In: AIAA Journal. - 1533-385X .- 0001-1452. ; 53:11, s. 3251-3272
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Journal article (peer-reviewed)abstract
- Large-eddy simulation is used to investigate steady-state mass flow injection into a supersonic jet stream with and without flapping motion of the microjets. The results are validated with particle image velocimetry and acoustic measurements. The effect of microjet penetration on the far-field acoustics is studied by altering the number of injectors, the cross-sectional area of each injector, and the injection mass flow. The injectors are evenly distributed around the nozzle exit. The injection angle is 90 deg relative to the main jet flow. This research is a continuation of a previous large-eddy simulation study of pulsed injection that showed that the unsteady injection-induced pressure pulses in the jet caused increased tonal noise for far-field observers at low angles. Flapping jet injection was shown to minimize the creation of the pressure pulses, except for high-amplitude flapping angles and high injection mass flows, where the injections divert out of the shear layer and introduce periodic superposition of the double shock-cell structure. Furthermore, the flapping injection did not show improved noise reduction compared with the steady injection, which is essentially promising because steady injection proves to be a more practical solution for implementation in real jet engine applications.
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| 11. |
- Hafsteinsson, Haukur, 1984, et al.
(author)
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Reduction of supersonic jet noise using micro-jets in the diverging part of a conical CD-nozzle
- 2015
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In: The International Conference on Jets, Wakes and Separated Flows (ICJWSF2015), June 16-18, 2015, Stockholm, Sweden.
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Conference paper (peer-reviewed)abstract
- Reducing the radiated noise from supersonic jets with maintainedthrust is a major challenge. An LES/CAA method and experiments are uti-lized to investigate the flow field and the far-field acoustics of a supersonic jetemitted from a circular CD-nozzle with a sharp throat. Air is injected into thedivergent section of the nozzle using 12 evenly distributed micro-jets aroundthe nozzle circumference and the change in total thrust and acoustic signa-ture is investigated. The micro-jets are shown to decrease shock-strength withincreased injection until an optimum point where further increase in injectionmass flow caused increased shock-strength. As a consequence of the reducedshock strength, the far-field shock-noise was decreased. The net thrust wasshown to increase with increased injection mass flow, whereas the specificthrust was slightly decreased. Micro-jet injection into the divergent sectionof a CD-nozzle appears, therefore, to be an effective configuration for reducedshock-noise radiation from supersonic jets.
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| 12. |
- Hafsteinsson, Haukur, 1984, et al.
(author)
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Supersonic Jet Excitation using Flapping Injection
- 2013
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In: American Physical Society, Division of Fluid Dynamics 66th Annual Meeting, November 24–26, 2013 Pittsburgh, Pennsylvania.
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Conference paper (other academic/artistic)abstract
- Supersonic jet noise reduction is important for high speed military aircraft. Lower acoustic levels would reduce structural fatigue leading to longer lifetime of the jet aircraft. It is not solely structural aspects which are of importance, health issues of the pilot and the airfield personnel are also very important, as high acoustic levels may result in severe hearing damage. It remains a major challenge to reduce the overall noise levels of the aircraft, where the supersonic exhaust is the main noise source for near ground operation. Fluidic injection into the supersonic jet at the nozzle exhaust has been shown as a promising method for noise reduction. It has been shown to speed up the mixing process of the main jet, hence reducing the kinetic energy level of the jet and the power of the total acoustic radiation. Furthermore, the interaction mechanism between the fluidic injection and the shock structure in the jet exhaust plays a crucial role in the total noise radia- tion. In this study, LES is used to investigate the change in flow structures of a supersonic (M=1.56) jet from a converging-diverging nozzle. Six fluidic actuators, evenly distributed around the nozzle exit, inject air in a radial direction towards the main flow axis with a total mass flow ratio of 3%. Steady injection is compared with flapping injection. With flapping injection turned on, the injection angle of each injector is varied sinusoidally in the nozzle exit plane and the variation is the same for all injectors. This fluid dynamics video is submitted to the APS DFD Gallery of Fluid Motion 2013 at the 66 the Annual Meeting of the American Physical Society, Division of Fluid Dynamics (24-26 November, Pittsburgh, PA, USA).
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| 13. |
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| 14. |
- Munday, D., et al.
(author)
-
Supersonic turbojet noise reduction
- 2013
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In: International Journal of Aeroacoustics. - 1475-472X. ; 12:3, s. 215-243
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Journal article (peer-reviewed)abstract
- Observations and Large Eddy Simulations are presented of a supersonic jet from a nozzle representative of high-performance military aircraft such as the Saab Gripen. The nozzle has a design Mach number of 1.56 and is examined at its design condition with a surrounding secondary flow at Mach numbers of 0.0, 0.1 and 0.3. The nozzle is investigated in its unmodified state and also with the addition of chevrons and microjets. Detailed flow-field velocity measurements of the jets and far-field noise measurements are presented and the noise results are scaled to represent the effects of the chevrons and microjets on airport neighbors. Chevrons and internal fluidic injection by microjets each reduce the noise generated by the main jet. And substantially reduce the noise footprint around the airport. The numerical simulation technique, correctly predicts the flow and noise not only the baseline case, but also the noise reduction by both chevrons and microjects.
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| 15. |
- Munday, D., et al.
(author)
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Techniques for supersonic turbojet noise reduction
- 2012
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In: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, GT 2012; Copenhagen; Denmark; 11 June 2012 through 15 June 2012. - 9780791844670 ; 1, s. 51-56
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Conference paper (peer-reviewed)abstract
- Observations and simulations are presented of a supersonic jet from a nozzle representative of high-performance military aircraft such as the Saab Gripen. The nozzle has a design Mach number of 1.56 and is examined at its design condition with a surrounding secondary flow at Mach numbers of 0.0, 0.1 and 0.3. Chevrons and internal fluidic injection by microjets each reduce the noise generated by the main jet. Copyright © 2012 by ASME.
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| 16. |
- Semlitsch, Bernhard, 1985-, et al.
(author)
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Transforming the Shock Pattern of Supersonic Jets using Fluidic Injection
- 2019
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In: AIAA Journal. - : American Institute of Aeronautics and Astronautics. - 0001-1452 .- 1533-385X. ; 57:5, s. 1851-1861
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Journal article (peer-reviewed)abstract
- Double shock diamonds establish in the exhaust of modular convergent–divergent nozzles. These consist of two shock structures: one originating from the nozzle throat, and another from its exit. Analyzing the shock pattern developing for different fluidic injection operating conditions, it is shown that fluidic injection allows the rearrangement of the shock structures relative to each other. Overlapping the two structures causes large pressure oscillations in the exhaust and high amplitudes of shock associated noise, whereas staggering the shock structures mitigates these effects. The screech tone frequency does not change for all injection operating configurations, although the shock diamonds are shifted drastically with respect to each other. Hence, the screech phenomenon is dominated by the primary shock spacing originating from the nozzle throat.
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