Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session G38: Acoustics III: Aero-Acoustics |
Hide Abstracts |
Chair: Ephraim Gutmark, University of Cincinnati Room: Sheraton Back Bay B |
Monday, November 23, 2015 8:00AM - 8:13AM |
G38.00001: Effect of an Adjacent Plate on Supersonic Jet Noise Ephraim Gutmark, Pablo Mora, Florian Baier, Kailas Kailasanath, Ryan Johnson, Kamal Viswanath A flat plate was installed parallel to Md = 1.5 circular and rectangular (AR=2) jets. Flow structures, from high speed shadowgraphs, and acoustic far-field at design, overexpanded and underexpanded conditions are compared between the free jets and the jets with the plate at different distances from the jet axis, 0.5-3De. The circular and rectangular jets had similar far field acoustics except that the latter had stronger screech tones. The free jet exhibited strong flapping mode and screech when overexpanded and broadband shock associated noise at all NPRs. When the plate was at the nozzle lip, the jet was stabilized and screech and BBSN were suppressed. Flapping and screech reappeared when the plate was moved away from the jet and at the largest stand off distance they were amplified. In the shielded region behind the plate, noise levels at all frequencies except the very low ones were significantly reduced for all plate positions. Conversely, reflection at the azimuthal angle above the plate enhanced OASPL magnitudes across all conditions. Mixing noise dominant in the downstream angle was affected by the plat location at the side azimuthal angle. The measurements were compared with LES computations of the SPL spectra and the OASPL and excellent agreement was shown. [Preview Abstract] |
Monday, November 23, 2015 8:13AM - 8:26AM |
G38.00002: Large-Eddy Simulations of Noise Generation in Supersonic Jets at Realistic Engine Temperatures Junhui Liu, Andrew Corrigan, K. Kailasanath, Brian Taylor Large-eddy simulations (LES) have been carried out to investigate the noise generation in highly heated supersonic jets at temperatures similar to those observed in high-performance jet engine exhausts. It is found that the exhaust temperature of high-performance jet engines can range from 1000K at an intermediate power to above 2000K at a maximum afterburning power. In low-temperature jets, the effects of the variation of the specific heat ratio as well as the radial temperature profile near the nozzle exit are small and are ignored, but it is not clear whether those effects can be also ignored in highly heated jets. The impact of the variation of the specific heat ratio is assessed by comparing LES results using a variable specific heat ratio with those using a constant specific heat ratio. The impact on both the flow field and the noise distributions are investigated. Because the total temperature near the nozzle wall can be substantially lower than the nozzle total temperature either due to the heating loss through the nozzle wall or due to the cooling applied near the wall, this lower wall temperature may impact the temperature in the shear layer, and thus impact the noise generation. The impact of the radial temperature profile on the jet noise generation is investigated by comparing results of lower nozzle wall temperatures with those of the adiabatic wall condition. [Preview Abstract] |
Monday, November 23, 2015 8:26AM - 8:39AM |
G38.00003: Numerical Simulations of Noise Generated by Supersonic Rectangular Jets. Part One: Validation. Kamal Viswanath, Ryan Johnson, Andrew Corrigan, Kazhikathra Kailasanath, Pablo Sanchez, Florian Baier, Ephraim Gutmark The noise from high performance jet engines of both civilian and military aircraft is an area of active concern. To date, much of the work on noise reduction techniques has focused on axisymmetric circular nozzles. Asymmetric exhaust nozzle configurations, in particular rectangular, are likely to become more important in the future. In this study we validate the far field noise for ideally and over expanded supersonic jets issuing from a low aspect ratio rectangular nozzle geometry. Validation of the acoustic data is performed against experimentally recorded sound pressure level (SPL) spectra for a host of observer locations around the asymmetric nozzle. Data is presented for the cold jet case and two heated jets for all nozzle pressure ratios. It is shown that elevated operating temperatures result in elevated sound levels across the frequency spectra at all locations. Screech tones, that are present for certain cases, diminish in amplitude or cease completely as the jet is heated. [Preview Abstract] |
Monday, November 23, 2015 8:39AM - 8:52AM |
G38.00004: Numerical Simulations of Noise Generated by Supersonic Rectangular Jets Part 2: Frequency Band Analysis of Far-field Noise Ryan Johnson, Kamal Viswanath, Kazhikathra kailasanath A method has been developed to analyze the asymmetry of far-field noise generated by rectangular jets by examining the contributions arising from different frequency bands. This method was used to analyze simulations of a supersonic jet issuing from a rectangular nozzle with aspect ratio of 2.0 at four frequency ranges for several over-expanded, cold jet scenarios. Results show that low frequency phenomenon, such as shear layer noise, contribute the most to the asymmetry of rectangular jet noise for these conditions. This method is being extended to examine the differences in asymmetry in comparable circular jets, as well as heated rectangular jets. [Preview Abstract] |
Monday, November 23, 2015 8:52AM - 9:05AM |
G38.00005: Flow Structures and Noise Produced by a Heated Rectangular Nozzle with a Third Stream and Aft Deck Christopher Ruscher, Sivaram Gogineni, Barry Kiel Jet noise is a huge issue that affects both civilian and military aviation and is a two-fold problem. Near-field noise causes hearing damage and is of great concern to the Navy. Far-field noise is also a concern for military and civilian aircraft. For military jets, the trend has shown that newer and more advanced planes are louder than their predecessors. Most of these planes are designed keeping the performance as the main driver in mind while the jet noise becomes an afterthought. To remedy this and to aid the design process, we propose to create a joint noise and performance prediction tool. To create this tool, one must understand how the near-field flow structures generate noise and how they are related to far-field noise. In the current work, we considered rectangular, three-stream nozzle with an aft deck and investigated the flow structures such as corner vortices, shocks and their impact on the noise generation mechanism. We have also used state-of-the-art data analytical tools such as wavelets, POD, and stochastic estimations. [Preview Abstract] |
Monday, November 23, 2015 9:05AM - 9:18AM |
G38.00006: The effects of heating on instability waves and noise in subsonic jets Zhenhua Wan, Haihua Yang, Xingchen Zhang, Dejun Sun We performed large eddy simulation(LES) for two subsonic transitional jets, i.e. a cold jet and its heated counterpart, with a relatively high Reynolds number. In the far field, the noise radiation at small aft angles is enhanced by heating, while the noise intensity at large angles to jet axis is reduced. The noise enhancement at small aft angles might be attributed to the change of the evolution of instability wave. Based on LES mean flow, the $N$- factors are obtained by solving linear parabolized stability equations(PSE), which shows that the peaks of $N$-factors move upstream and $m=0$ mode is mostly influenced due to heating. From $N$-factor, it is also known that the dominant instability waves in both jets should be produced by nonlinear interaction. For better understanding such nonlinear process, the nonlinear interaction model (NIM) based on PSE solution and acoustic analogy is evaluated carefully by comparing the model results with that of simulation. It is found that NIM gives relatively reasonable radiation pattern for $m=0$ mode in both jets, but less satisfactory results are obtained for higher $m$ modes. [Preview Abstract] |
Monday, November 23, 2015 9:18AM - 9:31AM |
G38.00007: Sensitivity of wavepackets in jets to non-linear effects: the role of the critical layer Gilles Tissot, Mengqi Zhang, Francisco C. Laj\'us Jr., Andr\'e V. G. Cavalieri, Peter Jordan, Tim Colonius Linear instability waves, or wavepackets, are key building blocks for the jet-noise problem. It has been shown in previous work that linear models correctly predict the evolution of axisymmetric wavepackets up to the end of the potential core of subsonic turbulent jets. Beyond this station linear models fail, and non-linearity is the likely missing piece. The essential underlying nonlinear mechanisms are unknown, and it remains unclear how these should be incorporated in a reduced-order model. The non-linear interactions are considered in this work as an ``external'' harmonic forcing added to the standard linear model. This modelling framework is explored using three complementary problems: a direct forcing, a resolvant analysis and a 4D-Var data assimilation approach. In all of the problems considered, the critical layer is found to be relevant: it is the position where the sensitivity of the linear waves to non-linearity is greatest. Furthermore, forced perturbations are tilted by shear, in a manner that suggests an Orr-like mechanism. The ensemble of results suggest that the critical layer may play a central role in the modelling of wavepackets in subsonic turbulent jets, and indeed may be the key to remedying the shortcomings of linear reduced-order models. [Preview Abstract] |
Monday, November 23, 2015 9:31AM - 9:44AM |
G38.00008: Reduction of aerodynamic sound generated in a flow past an oscillating and a fixed cylinder in tandem Yuji Hattori The aerodynamic sound generated in a two-dimensional flow past an oscillating and a fixed circular cylinder in tandem is studied. This flow can be regarded as a simplified model of the sound generation due to the interaction of rotating wings and a strut. The sound pressure is captured by direct numerical simulation of the compressible Navier-Stokes equations using the volume penalization method modified by the author. It is shown that synchronization plays a crucial role in sound reduction. When the frequency of the oscillating cylinder is smaller than that of vortex shedding of the fixed cylinder, the sound is significantly reduced due to synchronization as the frequency of vortex shedding is decreased. Sound reduction also depends on the distance between the cylinders. There are distances at which the forces exerted on the cylinders are in anti-phase so that the total force and thereby the resulting sound are significantly reduced. [Preview Abstract] |
Monday, November 23, 2015 9:44AM - 9:57AM |
G38.00009: Large Eddy Simulation of Airfoil Self-Noise at High Reynolds Number Joseph Kocheemoolayil, Sanjiva Lele The trailing edge noise section (Category 1) of the Benchmark Problems for Airframe Noise Computations (BANC) workshop features five canonical problems. No first-principles based approach free of empiricism and tunable coefficients has successfully predicted trailing edge noise for the five configurations to date. Our simulations predict trailing edge noise accurately for all five configurations. The simulation database is described in detail, highlighting efforts undertaken to validate the results through systematic comparison with dedicated experiments and establish insensitivity to grid resolution, domain size, alleatory uncertainties such as the tripping mechanism used to force transition to turbulence and epistemic uncertainties such as models for unresolved near-wall turbulence. Ongoing efforts to extend the predictive capability to non-canonical configurations featuring flow separation are summarized. A novel, large-span calculation that predicts the flow past a wind turbine airfoil in deep stall with unprecedented accuracy is presented. The simulations predict airfoil noise in the near-stall regime accurately. While the post-stall noise predictions leave room for improvement, significant uncertainties in the experiment might preclude a fair comparison in this regime. [Preview Abstract] |
Monday, November 23, 2015 9:57AM - 10:10AM |
G38.00010: Acoustic Scattering by a Vortex Dipole Zhongquan Zheng, Junjian Zhang Acoustic scattering in vortical flow has been an interesting and practical topic, with applications in problems such as acoustic scattering of turbulent flow. In this study, the linearized Euler equation model is employed to investigate sound wave propagation over a subsonic counter-rotating vortex dipole. Both the stationary and moving due to mutual induction vortex dipoles are studied. The numerical scheme uses a high-order WENO scheme to accommodate the highly convective background flow at high Mach numbers. The simulation results are compared with the analytical solutions and literature data. The theoretical study is focused on the effects of three characteristic length scales in this problem: the incident sound wave length, the vortex core size, and the vortex dipole size. The directivity and scaling laws related to the vortex scattering effects are discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700