Blade-vortex Interaction Noise Generation and Directionality PDF Download
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Author: Wel-Chong Sim
Publisher:
ISBN:
Category :
Languages : en
Pages : 360
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Author: Wel-Chong Sim
Publisher:
ISBN:
Category :
Languages : en
Pages : 360
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Author: Todd Darwin Ringler
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ISBN:
Category :
Languages : en
Pages : 332
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Author: See-Ho Wong
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Category :
Languages : en
Pages :
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Author: M. C. Joshi
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Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
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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).
Author: Henry E. Jones
Publisher:
ISBN:
Category : Unsteady flow (Aerodynamics)
Languages : en
Pages : 96
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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: Juan Abelló
Publisher:
ISBN:
Category :
Languages : en
Pages : 466
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Author: Romuald Morvant
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 199
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 32
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Author: Earl R. Booth
Publisher:
ISBN:
Category : Flow visualization
Languages : en
Pages : 32
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