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Helicopter rotor wake geometry and its influence in forward flight. Volume 1: Generalized wake geometry and wake effect on rotor airloads and performanceAn analytic investigation to generalize wake geometry of a helicopter rotor in steady level forward flight and to demonstrate the influence of wake deformation in the prediction of rotor airloads and performance is described. Volume 1 presents a first level generalized wake model based on theoretically predicted tip vortex geometries for a selected representative blade design. The tip vortex distortions are generalized in equation form as displacements from the classical undistorted tip vortex geometry in terms of vortex age, blade azimuth, rotor advance ratio, thrust coefficient, and number of blades. These equations were programmed to provide distorted wake coordinates at very low cost for use in rotor airflow and airloads prediction analyses. The sensitivity of predicted rotor airloads, performance, and blade bending moments to the modeling of the tip vortex distortion are demonstrated for low to moderately high advance ratios for a representative rotor and the H-34 rotor. Comparisons with H-34 rotor test data demonstrate the effects of the classical, predicted distorted, and the newly developed generalized wake models on airloads and blade bending moments. Use of distorted wake models results in the occurrence of numerous blade-vortex interactions on the forward and lateral sides of the rotor disk. The significance of these interactions is related to the number and degree of proximity to the blades of the tip vortices. The correlation obtained with the distorted wake models (generalized and predicted) is encouraging.
Document ID
19840009081
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Egolf, T. A. (United Technologies Research Center East Hartford, CT, United States)
Landgrebe, A. J. (United Technologies Research Center East Hartford, CT, United States)
Date Acquired
September 4, 2013
Publication Date
October 1, 1983
Subject Category
Aerodynamics
Report/Patent Number
UTRC/R83-912666-58-VOL-1
NASA-CR-3726
NAS 1.26:3726
AD-A135555
Accession Number
84N17149
Funding Number(s)
CONTRACT_GRANT: NAS1-14568
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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