You are here

FAU Collections » FAU Research Repository » FAU Theses and Dissertations

Effects of rotating frame turbulence and dynamic stall on gust response of helicopter blades

Download pdf | Full Screen View

Date Issued:
1990
Summary:
Rotating frame turbulence, or RFT, refers to the actual turbulence experienced by the helicopter blades and requires noneulerian description and rotational sampling of measurements. In the stationary case of axial flight, as investigated earlier, its spectra has peaks centered at integer multiples of rotational speed P, as in wind turbines. In forward flight, as investigated here, its instantaneous or frequency-time spectra has split peaks centered at P/2, P, 3P/2, 2P etc. Though nonstationary, it is wide sense cyclostationary in that its autocorrelation function R(t1,t2) = R(t1 + 2m pi, t2 + 2n pi) for integers m = n only. The major RFT characteristics--spectral peaks, the consequent transfer of energy essentially from the low-frequency region (<1P) to the high-frequency region (>1P) and cyclostationarity--cannot be predicted by conventional space-fixed description. However, these characteristics are simultaneously predicted by the instantaneous spectra, and for their qualitative and parametric investigation, a closed-form solution of an instantaneous spectrum is presented for a space-fixed turbulence model. The RFT effects on the blade response statistics of rms values and average threshold crossing rates are presented as well. The blade model includes flap bending degrees of freedom and dynamic stall effects. The blade response statistics demonstrate that RFT effects are appreciable for low-advance ratio and low-altitude flight conditions and that dynamic stall increases gust sensitivity.
Title: Effects of rotating frame turbulence and dynamic stall on gust response of helicopter blades.
81 views
32 downloads
Name(s): Madhavan, R.
Florida Atlantic University, Degree grantor
Gaonkar, Gopal H., Thesis advisor
College of Engineering and Computer Science
Department of Ocean and Mechanical Engineering
Type of Resource: text
Genre: Electronic Thesis Or Dissertation
Issuance: monographic
Date Issued: 1990
Publisher: Florida Atlantic University
Place of Publication: Boca Raton, Fla.
Physical Form: application/pdf
Extent: 134 p.
Language(s): English
Summary: Rotating frame turbulence, or RFT, refers to the actual turbulence experienced by the helicopter blades and requires noneulerian description and rotational sampling of measurements. In the stationary case of axial flight, as investigated earlier, its spectra has peaks centered at integer multiples of rotational speed P, as in wind turbines. In forward flight, as investigated here, its instantaneous or frequency-time spectra has split peaks centered at P/2, P, 3P/2, 2P etc. Though nonstationary, it is wide sense cyclostationary in that its autocorrelation function R(t1,t2) = R(t1 + 2m pi, t2 + 2n pi) for integers m = n only. The major RFT characteristics--spectral peaks, the consequent transfer of energy essentially from the low-frequency region (<1P) to the high-frequency region (>1P) and cyclostationarity--cannot be predicted by conventional space-fixed description. However, these characteristics are simultaneously predicted by the instantaneous spectra, and for their qualitative and parametric investigation, a closed-form solution of an instantaneous spectrum is presented for a space-fixed turbulence model. The RFT effects on the blade response statistics of rms values and average threshold crossing rates are presented as well. The blade model includes flap bending degrees of freedom and dynamic stall effects. The blade response statistics demonstrate that RFT effects are appreciable for low-advance ratio and low-altitude flight conditions and that dynamic stall increases gust sensitivity.
Identifier: 14613 (digitool), FADT14613 (IID), fau:11408 (fedora)
Collection: FAU Electronic Theses and Dissertations Collection
Note(s): College of Engineering and Computer Science
Thesis (M.S.E.)--Florida Atlantic University, 1990.
Subject(s): Helicopters--Aerodynamics
Held by: Florida Atlantic University Libraries
Persistent Link to This Record: http://purl.flvc.org/fcla/dt/14613
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.