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Frequency-time spectral analysis of helicopter turbulence and response in forward flight
| Title: | Frequency-time spectral analysis of helicopter turbulence and response in forward flight. |
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| Name(s): |
Vellathottam, George V. Florida Atlantic University, Degree grantor Gaonkar, Gopal H., Thesis advisor College of Engineering and Computer Science Department of Ocean and Mechanical Engineering |
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| Type of Resource: | text | |
| Genre: | Electronic Thesis Or Dissertation | |
| Issuance: | monographic | |
| Date Issued: | 1991 | |
| Publisher: | Florida Atlantic University | |
| Place of Publication: | Boca Raton, Fla. | |
| Physical Form: | application/pdf | |
| Extent: | 144 p. | |
| Language(s): | English | |
| Summary: | 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,·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. | |
| Identifier: | 14683 (digitool), FADT14683 (IID), fau:11474 (fedora) | |
| Collection: | FAU Electronic Theses and Dissertations Collection | |
| Note(s): |
College of Engineering and Computer Science Thesis (M.S.E.)--Florida Atlantic University, 1991. |
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| Subject(s): |
Turbulence Rotors (Helicopters) |
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| Held by: | Florida Atlantic University Libraries | |
| Persistent Link to This Record: | http://purl.flvc.org/fcla/dt/14683 | |
| Sublocation: | Digital Library | |
| Use and Reproduction: | Copyright © is held by the author, with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder. | |
| Use and Reproduction: | http://rightsstatements.org/vocab/InC/1.0/ | |
| Host Institution: | FAU | |
| Is Part of Series: | Florida Atlantic University Digital Library Collections. |
