Search

航空宇宙技術研究所 7-9 Oct. 1998 (23th). 24-26 Mar. 1999 (24th) 東京 日本, National Aerospace Laboratory 7-9 Oct. 1998 (23th). 24-26 Mar. 1999 (24th) Tokyo Japan, 以下の主題について論じた。チャネル流遷移、3次元不安定性、衝撃自由剪断層不安定性、回転ゲルトラー流れ、e(exp N)法、斜め円柱境界層、縮流胴境界層遷移、回転円盤流、横流れ渦、絶対不安定性、圧縮性縦渦、超音速剪断層、衝撃波-境界層干渉、超音速境界層、小型超音速実験機、内部渦構造、2次渦、表面圧力変動、空音力強度、乱流境界層、円柱渦、剥離制御、等方性乱流、摩擦抵抗低減、小型超音速風洞、および強制磁気再結合。, The following topics are discussed: channel flow transition, three dimensional instability, impinging free shear layer instability, rotating Goertler flow, e(exp N) method, yawed cylinder boundary layer, laminar-turbulent transition, rotating disk flow, cross flow vortex, absolute instability, compressive streamwise vortex, supersonic shear layer, shock-boundary layer interaction, supersonic boundary layer, scaled supersonic experimental airplane, internal vortical structure, secondary vortex, surface pressure fluctuation, acoustic intensity, turbulent boundary layer flow, columnar vortex, control of separation, isotropic turbulence, friction drag reduction, supersonic wind tunnel, and forced magnetic reconnection., 資料番号: AA0001960000, レポート番号: NAL SP-43

航空宇宙技術研究所 7-9 Oct. 1998 (23th). 24-26 Mar. 1999 (24th) 東京 日本, National Aerospace Laboratory 7-9 Oct. 1998 (23th). 24-26 Mar. 1999 (24th) Tokyo Japan, 流線曲率モードより横流れ進行モードを分離するため、円盤上の孔から点源撹乱を導入した静止空気中の回転円盤流の実験的研究を行った。実験結果は、両方のモードの明確な分離が、点源の下流の楔状領域で、分散関係に従って現れることを示していた。また、増幅していく撹乱の特性については、複素特性曲線法を用いた線形安定性理論とよく一致した。本論文の最後では、斜め円柱の場合と比較として、なぜ回転円盤流や後退翼では、横流れ不安定の定在モードが支配的となりがちなのかを議論した。, An experimental investigation in rotating-disk flow in still air was made to separate the crossflow traveling mode from the streamline-curvature mode introducing a point-source disturbance through a hole on the disk. The experimental results show that the definite separation of both modes appeared in wedge-shaped region downstream of the point source in accordance with the dispersion relation. It is also shown that the characteristic features of growing disturbances are in good agreement with the linear stability theory making use of the method of complex characteristics. In the last part of this paper, the reason is discussed why the stationary mode of the crossflow instability is prone to dominant appearance on rotating disk and swept wing compared to yawed circular cylinder., 資料番号: AA0001960006, レポート番号: NAL SP-43

Characteristic features of a wave packet in a rotating-disk boundary layer were experimentally investigated. The point disturbance originating from a small hole on the disk forms an isolated wave packet which consists of two types of unstable waves. Comparison with the prediction by Itoh's linear stability theory enabled the identification of these waves; the streamline-curvature (S-C) modes with the smaller wave number in the circumferential direction and the higher frequency are observed prior to the appearance of cross-flow (C-F) modes with the larger wave number and lower frequency. The hot-wire analyses quantitatively show that such characteristic features of these modes are in good agreement with the theoretical results. Time trace of the edge of packet does not indicate the occurrence of absolute instability but shows that the wave packet convectively passes through the radius line corresponding to the critical Reynolds number for the absolute instability predicted by Lingwood., 資料番号: AA0045947029, レポート番号: NAL SP-56

Behavior of stationary vortices in rotating-disk boundary layer was experimentally investigated by hot-wire measurements. Sources of disturbance such as the disk vibration and free convection around the disk seem to affect the unsteadiness of the stationary vortices. The circumferential wave numbers and the position of vortices fluctuate for each rotation. The fluctuation was quantitatively evaluated. Small roughness elements have the effect of lowering the fluctuation although the nonlinear growth of the vortices becomes significant. This fact implies that the development of nonlinearity is not main cause of the unsteady behavior of the stationary vortices., 資料番号: AA0045947016, レポート番号: NAL SP-56

航空宇宙技術研究所 27-29 Sept.2000 東京 日本, National Aerospace Laboratory 27-29 Sept.2000 Tokyo Japan, 局所化した撹乱により起こる回転円板流中の3次元境界層の層流から乱流への遷移過程を実験的に検討した。熱線解析の結果は、点撹乱が乱流パッチに発達することを示した。くさび領域内で伝播する乱流パッチは、いわゆる直交流と流線曲率モードで構成される2種の進行波を伴う。乱流領域の平面形態の配置は三日月状でBlasius境界層における矢じり形乱流斑点とは異なる。, A laminar to turbulent transition process of a three-dimensional boundary layer in rotating-disk flow initiated by localized disturbances was experimentally investigated. The hot-wire analyses showed that the point disturbance develops into a turbulent patch. The turbulent patch propagating in the wedge region is accompanied by the two families of traveling waves, which consist of the so-called cross-flow and streamline-curvature modes. The configuration in the plane view of the turbulence region is a crescent, which is different from an arrowhead-shaped turbulent spot in a Blasius boundary layer., 資料番号: AA0028637007, レポート番号: NAL SP-48T

航空宇宙技術研究所 7-9 Oct. 1998 (23th). 24-26 Mar. 1999 (24th) 東京 日本, National Aerospace Laboratory 7-9 Oct. 1998 (23th). 24-26 Mar. 1999 (24th) Tokyo Japan, 回転円盤上の3次元境界層で絶対不安定が起こりうるかどうかを示すために、局所的でかつ伝播する波動撹乱について、複素特性曲線法による理論的な記述法を与えた。伝播理論における数値解は、従来の平行流理論の結果に反して、複素群速度の零点近傍では、撹乱の特別な増幅が起こらないことを示している。, A theoretical description of local and propagating-wave disturbances is made with the method of complex characteristics to show whether the absolute instability can occur in the three-dimensional boundary layer on rotating disk. Numerical solutions of the propagation theory indicate no particular amplification of disturbances near zeros of the complex group velocity in contradiction to results of the conventional parallel-flow theory., 資料番号: AA0001960009, レポート番号: NAL SP-43