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Preliminary Study of a Model Rotor in DescentWithin a program designed to develop experimental techniques for measuring the trajectory and structure of vortices trailing from the tips of rotor blades, the present preliminary study focuses on a method for quantifying the trajectory of the trailing vortex during descent flight conditions. This study also presents rotor loads and blade surface pressures for a range of tip-path plane angles and Mach numbers. Blade pressures near the leading edge and along the outer radius are compared with data obtained on the same model rotor, but in open jet facilities. A triangulation procedure based on two directable laser-light sheets, each containing an embedded reference, proved effective in defining the spatial coordinates of the trailing vortex. When interrogating a cross section of the flow that contains several trailing vortices, the greatest clarity was found to result when the flow is uniformly seeded. Surface pressure responses during blade-vortex interactions appeared equally sensitive near the leading edge and along the outer portion of the blade, but diminished rapidly as the distance along the blade chord increased. The pressure response was virtually independent of whether the tip-path plane angle was obtained through shaft tilt or cyclic pitch. Although the shape and frequency of the pressure perturbations on the advancing blade during blade-vortex interaction are similar to those obtained in open-jet facilities, the angle of the tip-path plane may need to be lower than the range covered in this study.
Document ID
20010038031
Acquisition Source
Ames Research Center
Document Type
Technical Memorandum (TM)
Authors
McAlister, K. W.
(Army Aviation and Missile Command Moffett Field, CA United States)
Tung, C.
(Army Aviation and Missile Command Moffett Field, CA United States)
Sharpe, D. L.
(Army Aviation and Missile Command Moffett Field, CA United States)
Huang, S.
(Army Aviation and Missile Command Moffett Field, CA United States)
Hendley, E. M.
(Army Aviation and Missile Command Moffett Field, CA United States)
Date Acquired
September 7, 2013
Publication Date
November 1, 2000
Subject Category
Aerodynamics
Report/Patent Number
A-99V0024
AFDD/TR-99-A-001
NAS 1.15:208785
NASA/TM-2000-208785
Funding Number(s)
PROJECT: RTOP 581-10-12
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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