Helicopter Blade-vortex Interaction Locations PDF Download
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Author: Danny R. Hoad
Publisher:
ISBN:
Category : Rotors (Helicopters)
Languages : en
Pages : 112
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Book Description
Author: Danny R. Hoad
Publisher:
ISBN:
Category : Rotors (Helicopters)
Languages : en
Pages : 112
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 64
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Author: Sudarshan N. Koushik
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Danny R. Hoad
Publisher:
ISBN:
Category :
Languages : en
Pages : 112
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Book Description
The results of a model rotor acoustic test in the Langley 4- by 7-Meter Tunnel are used to evaluate a free-wake analytical technique. An acoustic triangulation technique is used to locate the position in the rotor disk where the blade-vortex interaction noise originates. These locations, along with results of the rotor free-wake analysis, are used to define the geometry of the blade-vortex interaction noise phenomena as well as to determine if the free-wake analysis is a capable diagnostic tool. Data from tests of two teetering rotor systems are used in these analyses. Keywords; Helicopter rotor disks; Free wake; Blade-vortex interactions; Acoustic properties.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Author: Nikolaos Baltas
Publisher:
ISBN:
Category :
Languages : en
Pages : 794
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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: Sing Chu
Publisher:
ISBN:
Category :
Languages : en
Pages : 248
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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: Megan S. McCluer
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 51
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Book Description
