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Prediction And Measurement Of Blade Vortex Interaction Loading
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Book Synopsis Prediction and Measurement of Blade-Vortex Interaction Loading by :
Download or read book Prediction and Measurement of Blade-Vortex Interaction Loading written by and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: An extensive quantity of airload measurements was obtained for a pressure-instrumented model of the BO-105 main rotor for a large number of higher-harmonic control (HHC) settings at Duits-Nederlandse Wind Tunnel (DNW). The wake geometry, vortex strength, and vortex core size were also measured through a laser light sheet technique and LDV. These results are used to verify the BVI airload prediction methodologies developed by AFDD, DLR, NASA Langley, and ONERA. The comparisons show that an accurate prediction of the blade motion and the wake geometry is the most important aspect of the BVI airload predictions. (AN).
Book Synopsis HART-II: Prediction of Blade-Vortex Interaction Loading by :
Download or read book HART-II: Prediction of Blade-Vortex Interaction Loading written by and published by . This book was released on 2003 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the HART-I data analysis, the need for comprehensive wake data was found including vortex creation and aging, and its re-development after blade-vortex interaction. In October 2001, US Army AFDD, NASA Langley, German DLR, French ONERA and Dutch DNW performed the HART-II test as an international joint effort. The main objective was to focus on rotor wake measurement using a PIV technique along with the comprehensive data of blade deflections, airloads, and acoustics. Three prediction teams made preliminary correlation efforts with HART-II data: a joint US team of US Army AFDD and NASA Langley, German DLR, and French ONERA. The predicted results showed significant improvements over the HART-I predicted results, computed about several years ago, which indicated that there has been better understanding of complicated wake modeling in the comprehensive rotorcraft analysis. All three teams demonstrated satisfactory prediction capabilities, in general, though there were slight deviations of prediction accuracies for various disciplines.
Book Synopsis Prediction of Blade-vortex Interaction Noise Using Measured Blade Pressures by : M. C. Joshi
Download or read book Prediction of Blade-vortex Interaction Noise Using Measured Blade Pressures written by M. C. Joshi and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Predicting the High-frequency Airloads and Acoustics Associated with Blade-vortex Interaction by : Mary E. Kelly
Download or read book Predicting the High-frequency Airloads and Acoustics Associated with Blade-vortex Interaction written by Mary E. Kelly and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Full-Potential Modeling of Blade-Vortex Interactions by : Henry E. Jones
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.
Book Synopsis Effect of Wake Structure on Blade-Vortex Interaction Phenomena: Acoustic Prediction and Validation by :
Download or read book Effect of Wake Structure on Blade-Vortex Interaction Phenomena: Acoustic Prediction and Validation written by and published by . This book was released on 1995 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1996 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Effects of Vortex Modeling on Blade-Vortex Interaction Noise Prediction by :
Download or read book The Effects of Vortex Modeling on Blade-Vortex Interaction Noise Prediction written by and published by . This book was released on 1995 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of a blade vortex interaction noise prediction scheme, based on CAMRAD/JA, FPR and RAPP, quantifies the effects of errors and assumptions in the modeling of the helicopter's shed vortex on the acoustic predictions. CAMRAD/JA computes the wake geometry and inflow angles that are used in FPR to solve for the aerodynamic surface pressures. RAPP uses these surface pressures to predict the acoustic pressure. Both CAMRAD/JA and FPR utilize the Biot-Savart Law to determine the influence of the vortical velocities on the blade loading and both codes use an algebraic vortex model for the solid body rotation of the vortex core. Large changes in the specification of the vortex core size do not change the inplane wake geometry calculated by CAMRAD/JA and only slighty affect the out-of-plane wake geometry. However, the aerodynamic surface pressure calculated by FPR changes in both magnitude and character with small changes to the core size used by the FPR calculations. This in turn affects the acoustic predictions. Shifting the CAMRAD/JA wake geometry away from the rotor plane by 1/4 chord produces drastic changes in the acoustic predictions indicating that the prediction of acoustic pressure is extremely sensitive to the miss distance between the vortex and the blade and that this distance must be calulated as accurately as possible for acceptable noise predictions. The inclusion or exclusion of a vortex in the FPR-RAPP calculation allows for the determination of the relative importance of that vortex as a BVI noise source. (AN).
Book Synopsis Blade-vortex Interaction Noise Generation and Directionality by : Wel-Chong Sim
Download or read book Blade-vortex Interaction Noise Generation and Directionality written by Wel-Chong Sim and published by . This book was released on 1996 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Prediction of Blade-vortex Interaction Noise from Measured Blade Pressure by :
Download or read book Prediction of Blade-vortex Interaction Noise from Measured Blade Pressure written by and published by . This book was released on 1981 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis NASA Aerodynamics Program, Annual Report 1991 by :
Download or read book NASA Aerodynamics Program, Annual Report 1991 written by and published by . This book was released on 1992 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Note written by and published by . This book was released on 1974 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeronautical Engineering written by and published by . This book was released on 1971 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA)
Book Synopsis Treaties and Other International Acts Series by :
Download or read book Treaties and Other International Acts Series written by and published by . This book was released on 1946 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1967 with total page 742 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Book Synopsis NASA Scientific and Technical Publications by :
Download or read book NASA Scientific and Technical Publications written by and published by . This book was released on 1991 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
