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Author : Romuald Morvant
Publisher :
ISBN 13 :
Total Pages : 199 pages
Book Rating : 4.:/5 (567 download)
Download or read book The Investigation of Blade-vortex Interaction Noise Using Computational Fluid Dynamics written by Romuald Morvant and published by . This book was released on 2004 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781722428778
Total Pages : 60 pages
Book Rating : 4.4/5 (287 download)
Download or read book Helicopter Blade-Vortex Interaction Noise with Comparisons to Cfd Calculations written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-08 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comparison of experimental acoustics data and computational predictions was performed for a helicopter rotor blade interacting with a parallel vortex. The experiment was designed to examine the aerodynamics and acoustics of parallel Blade-Vortex Interaction (BVI) and was performed in the Ames Research Center (ARC) 80- by 120-Foot Subsonic Wind Tunnel. An independently generated vortex interacted with a small-scale, nonlifting helicopter rotor at the 180 deg azimuth angle to create the interaction in a controlled environment. Computational Fluid Dynamics (CFD) was used to calculate near-field pressure time histories. The CFD code, called Transonic Unsteady Rotor Navier-Stokes (TURNS), was used to make comparisons with the acoustic pressure measurement at two microphone locations and several test conditions. The test conditions examined included hover tip Mach numbers of 0.6 and 0.7, advance ratio of 0.2, positive and negative vortex rotation, and the vortex passing above and below the rotor blade by 0.25 rotor chords. The results show that the CFD qualitatively predicts the acoustic characteristics very well, but quantitatively overpredicts the peak-to-peak sound pressure level by 15 percent in most cases. There also exists a discrepancy in the phasing (about 4 deg) of the BVI event in some cases. Additional calculations were performed to examine the effects of vortex strength, thickness, time accuracy, and directionality. This study validates the TURNS code for prediction of near-field acoustic pressures of controlled parallel BVI. McCluer, Megan S. Ames Research Center...
Author : See-Ho Wong
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Computational Investigation of Blade Vortex Interaction Noise written by See-Ho Wong and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Roger C. Strawn
Publisher :
ISBN 13 :
Total Pages : 18 pages
Book Rating : 4.:/5 (317 download)
Download or read book New Computational Methods for the Prediction and Analysis of Helicopter Noise written by Roger C. Strawn and published by . This book was released on 1996 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise."
Author : Henry E. Jones
Publisher :
ISBN 13 :
Total Pages : 96 pages
Book Rating : 4.:/5 (317 download)
Download or read book Full-Potential Modeling of Blade-Vortex Interactions written by Henry E. Jones and published by . This book was released on 1997 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the full-potential modeling of a blade-vortex interaction was made. A primary goal of this study was to investigate the effectiveness of the various methods of modeling the vortex. The model problem restricts the interaction to that of an infinite wing with an infinite line vortex moving parallel to its leading edge. This problem provides a convenient testing ground for the various methods of modeling the vortex while retaining the essential physics of the full three-dimensional interaction. A full-potential algorithm specifically tailored to solve the blade-vortex interaction (BVI) was developed to solve this problem. The basic algorithm was modified to include the effect of a vortex passing near the airfoil. Four different methods of modeling the vortex were used: (1) the angle-of-attack methods, (2) the lifting-surface method, (3) the branch-cut method, and (4) the split-potential method. A side-by-side comparison of the four models was conducted. these comparisons included comparing generated velocity fields, a subcritical interaction, and a critical interaction. The subcritical and critical interactions are compared with experimentally generate results. The split-potential model was used to make a survey of some of the more critical parameters which affect the BVI.
Author :
Publisher :
ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.:/5 (946 download)
Download or read book Investigation of the Orthogonal Blade-Vortex Interaction written by and published by . This book was released on 2003 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Stereoscopic Particle Image Velocimetry (SPIV) system was developed and applied to measurements of the Orthogonal Blade-Vortex Interaction (BVI) in a wind tunnel. Measurements of the isolated vortex showed that the SPIV system could resolve the jet velocity profile within the vortex core to a reasonable accuracy, and views of the vortex from different sides of the wind tunnel showed similar velocity profiles. For the BVI measurements the SPIV system showed the existence of a strong.
Author : Earl P. N. Duque
Publisher :
ISBN 13 :
Total Pages : 20 pages
Book Rating : 4.:/5 (317 download)
Download or read book An Overset Grid Navier-Stokes/Kirchhoff-surface Method for Rotorcraft Aeroacoustic Predictions written by Earl P. N. Duque and published by . This book was released on 1996 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "This paper describes a new method for computing the flowfield and acoustic signature of arbitrary rotors in forward flight. The overall scheme uses a finite-difference Navier-Stokes solver to compute the aerodynamic flowfield near the rotor blades. The equations are solved on a system of overset grids that allow for prescribed cyclic and flapping blade motions and capture the interactions between the rotor blades and wake. The far-field noise is computed with a Kirchhoff integration over a surface that completely encloses the rotor blades. Flowfield data are interpolated onto this Kirchhoff surface using the same overset-grid techniques that are used for the flowfield solution. As a demonstration of the overall prediction scheme, computed results for far-field noise are compared with experimental data for both high-speed impulsive (HSI) and blade-vortex interaction (BVI) cases. The HSI case showed good agreement with experimental data while a preliminary attempt at the BVI case did not. The computations clearly show that temporal accuracy, spatial accuracy and grid resolution in the Navier-Stokes solver play key roles in the overall accuracy of the predicted noise. These findings will be addressed more closely in future BVI computations. Overall, the overset-grid CFD scheme provides a powerful new framework for the prediction of helicopter noise."
Author : David A. Caughey
Publisher : World Scientific
ISBN 13 : 9812703187
Total Pages : 466 pages
Book Rating : 4.8/5 (127 download)
Download or read book Frontiers of Computational Fluid Dynamics 2006 written by David A. Caughey and published by World Scientific. This book was released on 2005 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series of volumes to which this book belongs honors contributors who have made a major impact in computational fluid dynamics. This fourth volume in the series is dedicated to David Caughey on the occasion of his 60th birthday. The first volume was published in 1994 and was dedicated to Prof Antony Jameson. The second, dedicated to Earl Murman, was published in 1998. The third volume was dedicated to Robert MacCormack in 2002. Written by leading researchers from academia, government laboratories, and industry, the contributions in this volume present descriptions of the latest developments in techniques for numerical analysis of fluid flow problems, as well as applications to important problems in industry.
Author : Erkan Yildirim
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (847 download)
Download or read book Computational Study of High Speed Blade-vortex Interaction written by Erkan Yildirim and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents inviscid compressible simulations for the orthogonal blade-vortex interaction. A numerical model between the tail rotor of a helicopter and the trailing vortex system formed by the main rotor blades is assumed. The study takes a 'building-block' approach to investigating this problem. Firstly, the impulsive instantaneous blocking of the axial core flow by a flat plate is considered. In the second step, the three-dimensional gradual cutting of the vortex by a sharp flat-plate that moves at a finite speed through the vortex is performed. Finally the chopping of the vortex by a blunt leading edge aerofoil, which incorporates both the blocking effect and also the stretching and distortion of the vortex lines is studied. The solutions reveal that the compressibility effects are strong when the axial core flow of the vortex is impulsively blocked. This generates a weak shock-expansion structure propagating along the vortex core on opposite sides of the cutting surface. The shock and expansion waves are identified as the prominent acoustic signatures in the interaction. In a simplified, two-dimensional axisymmetric model, the modelling of the physical evolution of the vortex, including the evolution of the complex vortical structures that controls the vortex core size near the cutting surface, are studied. Furthermore, the three dimensional simulations revealed that there is a secondary and a tertiary noise sources due to compressibility effects at the blade leading edge and due to the shock-vortex interaction taking place on the blade, which is exposed to a transonic free-stream flow.
Author :
Publisher :
ISBN 13 :
Total Pages : 64 pages
Book Rating : 4.:/5 (317 download)
Download or read book Helicopter Blade-Vortex Interaction Noise with Comparisons to CFD Calculations written by and published by . This book was released on 1996 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 702 pages
Book Rating : 4.:/5 (31 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Nobuyuki Satofuka
Publisher : Springer Science & Business Media
ISBN 13 : 3642565352
Total Pages : 807 pages
Book Rating : 4.6/5 (425 download)
Download or read book Computational Fluid Dynamics 2000 written by Nobuyuki Satofuka and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 807 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings contain a selection of refereed contributions as a source of reference for all those interested in the state of the art in computational fluid dynamics. The conference brings together physicists, mathematicians and engineers to review and share recent advances in the field.
Author : Roxana Vasilescu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (575 download)
Download or read book Helicopter Blade Tip Vortex Modifications in Hover Using Piezoelectrically Modulated Blowing written by Roxana Vasilescu and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Aeroacoustic investigations regarding different types of helicopter noise have indicated that the most annoying noise is caused by impulsive blade surface pressure changes in descent or forward flight conditions. Blade Vortex Interaction (BVI) is one of the main phenomena producing significant impulsive noise by the unsteady fluctuation in blade loading due to the rapid change of induced velocity field during interaction with vortices shed from previous blades. The tip vortex core structure and the blade vortex miss distance were identified as having a primary influence on BVI. In this thesis, piezoelectrically modulated and/or vectored blowing at the rotor blade tip is theoretically investigated as an active technique for modifying the structure of the tip vortex core as well as for increasing blade vortex miss distance. The mechanisms of formation and convection of rotor blade tip vortices up to and beyond 360 degrees wake age are described based on the CFD results for the baseline cases of a hovering rotor with rounded and square tips. A methodology combining electromechanical and CFD modeling is developed and applied to the study of a piezoelectrically modulated and vectored blowing two-dimensional wing section. The thesis is focused on the CFD analysis of rotor flow with modulated tangential blowing over a rounded blade tip, and with steady mid-plane blade tip blowing, respectively. Computational results characterizing the far-wake flow indicate that for steady tangential blowing the miss distance can be doubled compared to the baseline case, which may lead to a significant reduction in BVI noise level if this trend shown in hover can be replicated in low speed forward flight. Moreover, near-wake flow analysis show that through modulated blowing a higher dissipation of vorticity can be obtained.
Author :
Publisher :
ISBN 13 :
Total Pages : 134 pages
Book Rating : 4.:/5 (227 download)
Download or read book A Free-Wake Euler and Navier-Stokes CFD Method and Its Application to Helicopter Rotors Including Dynamic Stall written by and published by . This book was released on 1993 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes the results of the research in two parts. Part I describes the development and application of a free-wake Euler and Navier- Stokes computational fluid dynamics method, called 'TURNS', for helicopter applications. This finite-difference, implicit, upwind numerical method uses structured grids, and has been used for calculating the viscous, three- dimensional flow-fields of rotors in hover, forward flight, blade-vortex interactions, and high speed impulsive noise. The good agreement of numerical results with experiments for surface pressures, wake trajectory, thrust, power, Figure of Merit, and acoustic wave forms indicate the accuracy and suitability of the numerical method. It is demonstrated that both aerodynamics and acoustics information can be obtained in a single solution of the governing equations. In Part II, the unsteady flowfield results of a two-dimensional oscillating wing are presented for five widely used turbulence models and compared with experiments. The accuracy and suitability of turbulence models for unsteady separated flow axe discussed. Free-wake, Hover, Viscous, Three-dimensional, Forward flight, Helicopter, Dynamic stall, Light-stall, Deep-stall, Unsteady, Euler, Navier-stokes, Blade-vortex interaction, Impulsive noise.
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781725071674
Total Pages : 38 pages
Book Rating : 4.0/5 (716 download)
Download or read book Aeroacoustic Research Programs at the Army Aviation Research and Technology Activity written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-10 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Army rotorcraft aeroacoustic programs are reviewed, highlighting the theoretical and experimental progress made by Army researchers in the physical understanding of helicopter impulsive noise. The two impulsive noise sources addressed over this past decade are high-speed impulsive noise and blade-vortex interaction noise, both of which have had and will continue to have an increasing influence on Army rotorcraft design and operations. The advancements discussed are in the areas of in-flight data acquisition techniques, small-scale-model tests in wind tunnels, holographic interferometry/tomographic techniques, and the expanding capabilities of computational fluid dynamics in rotorcraft acoustic problems. Current theoretical prediction methods are compared with experimental data, and parameters that govern model scaling are established. The very successful cooperative efforts between the Army, NASA, and industry are also addressed Yu, Yung H. and Schmitz, Fredric H. and Morse, H. Andrew Ames Research Center ...
Author : Gordon J. Leishman
Publisher : Cambridge University Press
ISBN 13 : 9780521858601
Total Pages : 860 pages
Book Rating : 4.8/5 (586 download)
Download or read book Principles of Helicopter Aerodynamics with CD Extra written by Gordon J. Leishman and published by Cambridge University Press. This book was released on 2006-04-24 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by an internationally recognized teacher and researcher, this book provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft such as tilt rotors and autogiros. The text begins with a unique technical history of helicopter flight, and then covers basic methods of rotor aerodynamic analysis, and related issues associated with the performance of the helicopter and its aerodynamic design. It goes on to cover more advanced topics in helicopter aerodynamics, including airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes, and rotor-airframe aerodynamic interactions, with final chapters on autogiros and advanced methods of helicopter aerodynamic analysis. Extensively illustrated throughout, each chapter includes a set of homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thoroughly revised and updated text on rotating-wing aerodynamics.
Author :
Publisher :
ISBN 13 :
Total Pages : 538 pages
Book Rating : 4.3/5 (91 download)
Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
