Transonic Effects on Aerodynamics and Acoustics of Blade-vortex Interaction PDF Download
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Author: Rajneesh K. Singh
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 532
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Book Description
Author: Rajneesh K. Singh
Publisher:
ISBN:
Category : Aerodynamics, Transonic
Languages : en
Pages : 532
Get Book Here
Book Description
Author: Rajneesh Singh
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Author: Rajneesh Singh
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722428778
Category :
Languages : en
Pages : 60
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Book Description
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:
Publisher:
ISBN:
Category :
Languages : en
Pages : 15
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Book Description
During the Higher Harmonic Control Aeroacoustic Rotor Test, extensive measurements of the rotor aerodynamics, the far-field acoustics, the wake geometry and the blade motion for powered, descent, flight conditions were made. These measurements have been used to validate and improve the prediction of blade-vortex interaction (BVI) noise. The improvements made to the BVI modeling after the evaluation of the test data are discussed. The effects of these improvements on the acoustic-pressure predictions are shown. These improvements include re-structuring the wake, modifying the core size, incorporating the measured blade motion into the calculations and attempting to improve the dynamic blade response. A comparison of four different implementations of the Ffowcs Williams and Hawkings equation is presented. A common set of aerodynamic input has been used for this comparison. (AN).
Author: Wel-Chong Sim
Publisher:
ISBN:
Category :
Languages : en
Pages : 360
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Book Description
Author: Henry E. Jones
Publisher:
ISBN:
Category : Unsteady flow (Aerodynamics)
Languages : en
Pages : 96
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Book Description
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: A. Krothapalli
Publisher: Springer Science & Business Media
ISBN: 146124840X
Category : Science
Languages : en
Pages : 511
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Book Description
The Joint Institute for Aeronautics and Acoustics at Stanford University was established in October 1973 to provide an academic environment for long-term cooperative research between Stanford and NASA Ames Research Center. Since its establishment, the Institute has conducted theoretical and experimental work in the areas of aerodynamics, acoustics, fluid mechanics, flight dynamics, guidance and control, and human factors. This research has involved Stanford faculty, research associates, graduate students, and many distinguished visitors in collaborative efforts with the research staff of NASA Ames Research Center. The occasion of the Institute's tenth anniversary was used to reflect back on where that research has brought us, and to consider where our endeavors should be directed next. Thus, an International Symposium was held to review recent advances in the fields relevant to the activities of the Institute and to discuss the areas of research to be undertaken in the future. This anniversary was also chosen as an opportunity to honor one of the Institute's founders and its director, Professor Krishnamurty Karamcheti. It has been his crea tive inspiration that has provided the ideal research environment at the Joint Institute.
Author: Mary E. Kelly
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
As a rotorcraft descends or manoeuvres, the interactions which occur between the rotorblades and vortical structures within the rotor wake produce highly impulsive loads onthe blades and with these a highly intrusive external noise. Brown?s Vorticity TransportModel has been used to investigate the influence of the fidelity of the local blade aerodynamicmodel on the quality of the prediction of the high-frequency airloads associated withblade-vortex interactions and thus on the accuracy with which the acoustic signature ofthe aircraft can be predicted. Aerodynamic, wake structure and acoustic predictions usingthe Vorticity Transport Model are compared against the HART II wind tunnel data for anexperimental rotor based on the characteristics of the Bo105 rotor. The model can resolvevery accurately the structure of the wake, and allows significant flexibility in the way thatthe blade loading can be represented. The predictions of two models for the local bladeaerodynamics are compared for all three of the HART II flight cases. The first model isa simple lifting-line model and the second is a somewhat more sophisticated lifting-chordmodel based on unsteady thin aerofoil theory. The predicted positions of the vortex coresagree with measured data to within a fraction of the blade chord, and the strength ofthe vortices is preserved to well downstream of the rotor, essentially independently of theresolution of the calculation or the blade model used. A marked improvement in accuracyof the predicted high-frequency airloads and acoustic signature of the HART II rotoris obtained when the lifting-chord model for the blade aerodynamics is used instead ofthe lifting-line type approach. Errors in the amplitude and phase of the loading peaks are reduced and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake. Predictions of the acoustic signature of the rotor are similarly affected, with the lifting-chord model at the highest resolution producing the best representation of the distribution of sound pressure on the ground plane below therotor.
Author: G. R. Srinivasan
Publisher:
ISBN:
Category :
Languages : en
Pages : 20
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Book Description
A computational procedure and some numerical results of unsteady interaction of a helicopter rotor blade with a Lamb-like vortex of finite viscous core in subsonic and transonic flows is presented. The interaction considered here is one of the limiting cases of a more complex interaction typically encountered on helicopter rotor blade. In this limit, the interacting flow field is considered to be unsteady but two-dimensional. Accordingly, unsteady, two-dimensional, thin-layer Navier-Stokes equations are solved using a prescribed-vortex method (also called perturbation method) for the cases of stationary and moving rotor blades encountering a moving vortex passing the blades. The numerical results are compared with the recent experimental data of Caradonna et al. for the latter case. The comparison shows that for the transonic cases, the flow field is dominated by the presence of the shock waves, with strong indications of unsteady time lags in the shock-wave motions and shock-wave strengths, and of important three-dimensional effects. For subcritical-flow cases, however, the unsteady lag effects on the basic rotor blade are absent, and three-dimensional effects appear to be negligible, unlike the supercritical case. The subcritical calculations are in good agreement with the experimental data.
