Current Search: Vellathottam, George V. (x)
-
-
Title
-
Frequency-time spectral analysis of helicopter turbulence and response in forward flight.
-
Creator
-
Vellathottam, George V., Florida Atlantic University, Gaonkar, Gopal H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
-
Abstract/Description
-
The atmospheric turbulence that a blade station experiences is called blade-fixed turbulence. It can qualitatively differ from the conventional body-fixed turbulence such as experienced by an element of the body or fuselage. This difference is due to the rotational ,-elocity, which causes fore-and-aft motions of the blade station through the turbulence waves. A closed-form solution of a frequency-time spectrum for the dominant vertical turbulence velocity at an arbitrary blade station is dc,...
Show moreThe atmospheric turbulence that a blade station experiences is called blade-fixed turbulence. It can qualitatively differ from the conventional body-fixed turbulence such as experienced by an element of the body or fuselage. This difference is due to the rotational ,-elocity, which causes fore-and-aft motions of the blade station through the turbulence waves. A closed-form solution of a frequency-time spectrum for the dominant vertical turbulence velocity at an arbitrary blade station is dc,·eloped. This solution makes it possible to explain qualitatively the turbulence cllcrgy transfer due to rotational velocity from the low-frequency region (< 1P or 1/ rcv.) to the high-frequency(> 1P) region with the occurrence of spectral peaks and split peaks at 1P /2, 1P, 3P /2, 2P etc. Comparison of blade responses to bladeand body-fixed turbulence is also presented over a comprehensive range of turbulcuce scale length and advance ratio; the comparison covers frequency-time spectra, correlations including standard deviations, and average threshold-crossing rates of a flapping blade. A major contribution is to formulate both the cyclostationary turbulence and blade response by the frequency-time spectra, which predict simultaneously the time- ancl frequency-dependent characteristics such as the energy culltained in the frequency and time intervals. For low-altitude and low-advanceratio flights, such as nap-of-the earth or NOE flights, rotational velocity effects on turbulence modeling qualitatively affect the prediction of turbulence ancl response statistics.
Show less
-
Date Issued
-
1991
-
PURL
-
http://purl.flvc.org/fcla/dt/14683
-
Subject Headings
-
Turbulence, Rotors (Helicopters)
-
Format
-
Document (PDF)
