Download or read book Sound Generated by Instability Wave shock cell Interaction in Supersonic Jets written by Prasun K. Ray and published by . This book was released on 2006 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computation of Shock Induced Noise in Imperfectly Expanded Supersonic Jets written by Bulent Imamoglu and published by . This book was released on 2004 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interaction of Sound from Supersonic Jets with Nearby Structures written by and published by . This book was released on 1997 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Numerical Investigation of Sound Generation in Supersonic Jet Screech written by Ted A. Manning and published by . This book was released on 1999 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interaction of Sound from Supersonic Jets with Nearby Structures written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-10-21 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model of sound generated in an ideally expanded supersonic (Mach 2) jet is solved numerically. Two configurations are considered: (1) a free jet and (2) an installed jet with a nearby array of flexible aircraft type panels. In the later case the panels vibrate in response to loading by sound from the jet and the full coupling between the panels and the jet is considered, accounting for panel response and radiation. The long time behavior of the jet is considered. Results for near field and far field disturbance, the far field pressure and the vibration of and radiation from the panels are presented. Panel response crucially depends on the location of the panels. Panels located upstream of the Mach cone are subject to a low level, nearly continuous spectral excitation and consequently exhibit a low level, relatively continuous spectral response. In contrast, panels located within the Mach cone are subject to a significant loading due to the intense Mach wave radiation of sound and exhibit a large, relatively peaked spectral response centered around the peak frequency of sound radiation. The panels radiate in a similar fashion to the sound in the jet, in particular exhibiting a relatively peaked spectral response at approximately the Mach angle from the bounding wall. Fenno, C. C., Jr. and Bayliss, A. and Maestrello, L. Langley Research Center NAS1-19480; RTOP 505-90-52-01...

Download or read book A Numerical Investigation of Sound Generation in Supersonic Jet Screech written by Ted A. Manning and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The noise of supersonic jet flows is due in part to the interaction between jet instability waves and the jet shock-cell structure. If no countermeasures are taken, the emitted shock-cell noise will re-excite certain instability wave modes at the nozzle lip and cause resonant feedback to occur. This feedback resonance, known as supersonic jet screech, causes the jet to flap violently at discrete frequencies and generate very strong, narrow banded tones. Jet screech has been shown to be a source of acoustic fatigue in the tail and nozzle structures of supersonic aircraft. It is important that methods for predicting the screech amplitude be developed. Screech sound generation is one such element. We isolate the interaction of an unsteady shear layer with a single oblique shock. To obtain an overall understanding of the phenomenon with fewest simplifications, we study this problem through the numerical solution of the Navier Stokes equations. We then consider idealizations which allow us to obtain a similar but wider range of results with specially linearized Euler equations. The findings of these r0sults motivate the use of geometric acoustics to describe the screech generation process. The Navier-Stokes and Euler simulations have revealed important details about the interaction process, how the acoustic field results, and why screech is so loud. The mechanism for sound production is found to be fundamentally different and more efficient when the instability waves are the large vortices typical of screech, than when they are small disturbances. Geometrical acoustics can be used to explain the leakage effect at high instability wave amplitude. We conclude that the mechanism for high amplitude screech generation is an unsteady modification to the velocity field by the instability waves that permits the incident shock to refract through the shear layer.

Download or read book Coherent Structure and Shock vortex Interaction in the Screeching Supersonic Jet written by Daniel Michael Mitchell and published by . This book was released on 2013 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: This body of work describes an experimental investigation into coherent structuresand aeroacoustic feedback loops in underexpanded supersonic jets. The work includes a study of additional error terms in Particle Image Velocimetry (PIV) measurements due to the presence of shock waves within the flow, a detailed campaign of acoustic and time-resolved schlieren measurements as well as planar PIV measurements.An error analysis is conducted for the application of PIV to shock containingflows. The effect of size distribution within a seed material on measured relaxationtime is examined, with polydisperse particles of the same median diameter shown to possess a significantly higher relaxation time than their monodisperse counterpartswhen measured via a PIV algorithm. The influence of a shock wave induced velocitygradient within a PIV interrogation window on the correlation function is also examinedusing the Noiseless Cross Correlation Function of Soria (2006). The presence ofa shock is shown to introduce an artificial fluctuation into the measurement of velocity.This fluctuation is a function of the shock position, shock strength, spatial ratioand particle distribution. When the shock is located at the middle of the window,the magnitude of the fluctuation increases monotonically with increasing spatial ratio,increases asymptotically with shock strength, and decreases for increasing particle polydispersity. When the shock is located at the upstream edge of the window, the magnitude of the artificial fluctuation is highest for intermediate spatial ratios, going to zero at infinitely high and low values. In this instance particle polydispersity acts to increase the magnitude of fluctuations in measured velocity. In both cases particlepolydispersity serves to broaden the PDF of measured velocity. For the theoreticalcases presented herein, with a shock located within the interrogation window, the rootmean square of the artificial velocity fluctuations reaches values in excess of 30% of the freestream velocity. For the specific experiments presented later in the work, themagnitude of the artificial velocity fluctuation is less than 10%.Both the schlieren technique and PIV are applied to the study of the instabilitymodes of screeching axisymmetric jets. Jets at four pressure ratios: NPR = [2.2,2.6, 3.4, 4.2] are studied, and the dominant modes identified as A2, B, C and Crespectively. Three distinct modes at NPR = 2.2 are identified, one axisymmetric andtwo lateral, with screech Strouhal numbers of 0.71, 0.51 and 0.2 respectively. At NPR = 2.6 a dominant lateral mode is identified with St = 0.42. This mode proves the leastamenable to measurement with the PIV technique, as the direction of lateral oscillation precesses around the axis somewhat randomly. Helical modes at NPR = 3.4 and 4.2 are studied, with St = 0.39 and 0.35 respectively. The presence of a large Mach disk at NPR = 4.2 is not shown to qualitatively change the dynamics of the screech process.The production of discrete acoustic tones by the interaction between embeddedshocks and convected vortices is directly visualized. The motion of vortices is seen tocreate a disturbance wave at the shock reflection point of an upstream shock cell, this disturbance convects to the jet core and forms the basis for an evanescent convecting shockwave downstream. The flattening of this shock wave during the passage of the vortex results in a strong acceleration of the shock-tip, which moves in a whip-like manner and generates a strong upstream travelling acoustic wave. Analysis of the skewness and kurtosis of the axial velocity probability density functions is shown to be able to identify locations of intense sound generation. The second, third and fourth shock cells are shown to be the dominant noise sources.

Download or read book Supersonic Jet Noise Generated by Large scale Instabilities written by John M. Seiner and published by . This book was released on 1982 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Computational Analysis of Supersonic Jet and Instability Wave Interaction written by Xin Zhang and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Supersonic Jet Noise Generated by Large scale Instabilities written by John M. Seiner and published by . This book was released on 1982 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Profiles on Supersonic Jet Noise written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-10-12 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of velocity profiles on supersonic jet noise are studied by using stability calculations made for a shock-free coannular jet, with both the inner and outer flows supersonic. The Mach wave emission process is modeled as the noise generated by the large scale turbulent structures or the instability waves in the mixing region. Both the vortex-sheet and the realistic finite thickness shear layer models are considered. The stability calculations were performed for both inverted and normal velocity profiles. Comparisons are made with the results for an equivalent single jet, based on equal thrust, mass flow rate and exit area to that of the coannular jet. The advantages and disadvantages of these velocity profiles as far as noise radiation is concerned are discussed. It is shown that the Rayleigh's model prediction of the merits and demerits of different velocity profiles are in good agreement with the experimental data. Tiwari, S. N. and Bhat, T. R. S. Unspecified Center NAG1-1581

Download or read book The Generation and Radiation of Supersonic Jet Noise Append 2 Shock associated noise data written by and published by . This book was released on 1972 with total page 694 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fluid Structure Sound Interactions and Control written by Yu Zhou and published by Springer. This book was released on 2018-05-15 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the proceedings of the Symposium on Fluid-Structure-Sound Interactions and Control (FSSIC), (held in Tokyo on Aug. 21-24, 2017), which largely focused on advances in the theory, experiments on, and numerical simulation of turbulence in the contexts of flow-induced vibration, noise and their control. This includes several practical areas of application, such as the aerodynamics of road and space vehicles, marine and civil engineering, nuclear reactors and biomedical science, etc. Uniquely, these proceedings integrate acoustics with the study of flow-induced vibration, which is not a common practice but can be extremely beneficial to understanding, simulating and controlling vibration. The symposium provides a vital forum where academics, scientists and engineers working in all related branches can exchange and share their latest findings, ideas and innovations – bringing together researchers from both east and west to chart the frontiers of FSSIC.

Download or read book Noise and Instability Waves in Supersonic Jets in the Proximity of Flat and Cylindrical Walls written by K.K. Ahuja and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fluid Structure Sound Interactions and Control written by Marianna Braza and published by Springer Nature. This book was released on 2021-05-05 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a thorough and unique record of recent advances in the important scientific fields fluid–structure interaction, acoustics and control of priority interest in the academic community and also in an industrial context regarding new engineering designs. It updates advances in these fields by presenting state-of-the-art developments and achievements since the previous Book published by Springer in 2018 after the 4th FSSIC Symposium. This book is unique within the related literature investigating advances in these fields because it addresses them in a complementary way and thereby enhances cross-fertilization between them, whereas other books treat these fields separately.

Download or read book Aircraft Noise written by Oleksandr Zaporozhets and published by CRC Press. This book was released on 2011-05-13 with total page 435 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft noise has adverse impacts on passengers, airport staff and people living near airports, it thus limits the capacity of regional and international airports throughout the world. Reducing perceived noise of aircraft involves reduction of noise at source, along the propagation path and at the receiver. Effective noise control demands highly skilled and knowledgeable engineers. This book is for them. It shows you how accurate and reliable information about aircraft noise levels can be gained by calculations using appropriate generation and propagation models, or by measurements with effective monitoring systems. It also explains how to allow for atmospheric conditions, natural and artificial topography as well as detailing necessary measurement techniques.

Download or read book Computational Fluid Dynamics 2002 written by Steve Armfield and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 837 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are pleased to present the Proceedings of the Second International Conference on Computational Fluid Dynamics held at the University of Sydney, Australia, from July 15 to 19, 2002. The conference was a productive meeting of scientists, mathematicians and engineers involved in the computation of fluid flow. Keynote lectures were presented in the areas of optimisation, algorithms, turbulence and bio-fluid mechanics. Two hundred and fifty abstracts from many countries were received for con sideration. The executive committee, consisting of A. Lerat, M. Napolitano, J.J. Chattot, N. Satofuka and myself, were responsible for the selection of papers. Each of the members had a separate subcommittee to carry out the evaluation. One hundred and seventy papers were selected of which one hundred and fifty two were presented at the conference. All papers that appear in the proceedings have been peer reviewed by a panel of experts (with a minimum of two for every paper) before publication. The conference was attended by 160 delegates with a minimum of late with drawals. The informal and friendly atmosphere provided by the university sur roundings was highly appreciated, and the technical aspects of the conference were stimulating. It is appropriate here to thank Alain Lerat, the retiring secretary of the international scientific committee of the conference. We also wish to welcome J. J. Chattot who is the incoming secretary.