回転翼の安定に及ぼす大気乱流の影響(1)-フラッピングとフラピング-捩れの連成振動- : EFFECT OF ATMOSPHERIC TURBULENCE ON THE STABILITY OF A LIFTING ROTOR BLADE(I), FLAP AND COUPLED FLAP-TORSION MOTIONS

• Material Type: 文書・図像類
• Title: 回転翼の安定に及ぼす大気乱流の影響(1)-フラッピングとフラピング-捩れの連成振動- : EFFECT OF ATMOSPHERIC TURBULENCE ON THE STABILITY OF A LIFTING ROTOR BLADE(I), FLAP AND COUPLED FLAP-TORSION MOTIONS
• Author/Editor: 藤森, 義典; FUJIMORI, Yoshinori
• Author Heading: 藤森, 義典; FUJIMORI, Yoshinori
• Publication, Distribution, etc.: 航空宇宙技術研究所
• Publication Date: 1980-02
• Publication Date (W3CDTF): 1980-02
• Periodical title: 航空宇宙技術研究所報告 = Technical Report of National Aerospace Laboratory TR-599
• No. or year of volume/issue: 599
• Volume: 599
• Pages: 36-
• ISSN (Periodical Title): ISSN : 0389-4010
• Text Language Code: jpn
• Target Audience: 一般
• Note (General): 回転翼ブレードが3次元大気乱流中を飛行するとき,ブレードの運動がどのような影響を受けるかを明らかにしたものである。ブレードの運動として(1)フラッピングのみと,(2)フラッピングと捩れの連成系,の2ケの場合を考え,両者が3次元大気乱流中では係数励振型の微分方程式でモデル化されることを示した。これらの力学系の安定問題を解くための道具として,統計的平均法とFloquetの遷移行列計算を組合せた一般的方法を提案した。数値計算例からフラッピングモードのみはほとんど大気乱流の影響を受けないとしてよいこと,フラッピングと捩れの連成運動では高速飛行時にその安定性がかなり低下することなどが明らかとなった。; The purpose of this study is to investigate the motion stability of a lifting rotor blade operating in a turbulent flow. Such a blade may be used in a helicopter or other rotorcrafts and the turbulent flow may be a natural phenomenon or one generated by vortices of other blades. In order to achieve this goal, a procedure is developed in which use is made of the Markov process theory and the numerical solution of the Floquet transition matrix and its eigenvalues. This study is carried out through the following steps: 1)Derivation of equations governing the flap and flap-torsion motions of a blade operating in a three-dimensional turbulent flow field. All three turbulent velocity components are taken into consideration in the formulation. 2)Determination of stochastic stability boundaries in terms of the first and second moments of blade angular deflections and their derivatives for the flap motion and the coupled flap-torsion motion. It is found that terms involving the two horizontal turbulence components appear in the coefficients of the uncoupled flap and the coupled flap-torsion equations. Thus these terms play the role of parametric excitation, and when the turbulence level is high the rotor blade can become unstable. On the other hand, the vertical turbulence component contributes only a purely external force to the uncoupled flap and the coupled flap-torsion equations. Since the aerodynamic damping for the torsional motion vanishes in the reversed flow region, the stability of the coupled flap-torsion motion is dominated by the torsion mode, especially during a high forward velocity flight. The basic differential equations governing the flap and flap-torsion motions are first linearized and then converted into corresponding stochastic differential equations in the sense of Ito. For simplicity, all parametric excitations are assumed to be of the white noise type with constant spectral densities. In this case, the conversion can be accomplished by adding the correction terms of Wong and Zakai. The equations for the first moments follow directly from taking ensemble averages of the Ito stochastic differential equations. Derivation of the second moment equations is carried out through the following two steps: 1)obtain another set of Ito equations for the second powers and products of the response components by use of Ito’s Lemma, and 2)take the ensemble averages of those equations. Since both the first and second moment equations are differential equations with periodic coefficients, the stability boundary in each case is found by a numerical search involving the determination of the Floquet transition matrix and its eigenvalues. The analytical solution of the uncoupled flap motion, obtained for the very low advance ratios, affirms that the lap mode remains very stable under normal circumstances. Numerical examples for two advance ratios, 2.4 for the uncoupled flap motion and 1.6 for the coupled flap-torsion motion, are given to illustrate the general theory. As expected the first moment stability condition is always implied by the second moment stability condition, which could have been proved by use of the Schwartz inequality. For normal turbulence intensities the boundaries for the first moment stability of the flap and the flap-torsion motions, and the boundary for the second moment stability of the flap motion alone do not deviate much from the baseline(i.e., stability boundary under non-turbulence condition). However, the second moment stability for the coupled flap-torsion motion deteriorates substantially when turbulence is present in the atmosphere. When we consider the effect of the one-dimensional turbulence, the second moment stability of the flap and flap-torsion motions are most sensitive to the turbulence in the lateral and longitudinal directions, respectively.; 資料番号: NALTR0599000; レポート番号: NAL TR-599
• Source: https://jaxa.repo.nii.ac.jp/?action=repository_action_common_download&item_id=44853&item_no=1&attribute_id=31&file_no=1
• Access Restrictions: 限定公開
• Data Provider (Database): 国立情報学研究所 : 学術機関リポジトリデータベース（IRDB）（機関リポジトリ）; https://irdb.nii.ac.jp
• Original Data Provider (Database): 宇宙航空研究開発機構 : 宇宙航空研究開発機構リポジトリ