並列タイトル等Flow-Field in a Vortex with Breakdown above Sharp Edged Delta Wings
タイトル（掲載誌）航空宇宙技術研究所報告 = Technical Report of National Aerospace Laboratory TR-423
一般注記This paper describes the behavior of vortex-flow, accompanied with breakdown, formed above sharp-edged dalta wings, which has been investigated experimentally as well as theoretically at NAL. Emphasis is placed particularly on the criterion for the breakdown at sufficiently large Reynolds numbers. First, shown are the mean velocity components Ux, Uy, Ur, and the total head Hc along the vortex axis measured in the vortex-flow field over three flat-plate delta wing models with apex angles of 40deg, 50deg, and 60deg. Experimental data are conveniently non-dimensionalized in terms of the maximum velocity Uo and the distance L, at which the velocity along the vortex axis becomes half of Uo. These results show that the pronounced effect of the vortex breakdown presents itself on the mean axial-velocity distribution across the vortex and the total head change along the vortex central axis. The breakdown point can therefore be determined from the criterion dHc/dx=0 or(∂2Ux/∂R2)R=0=0 The spiral form of the vortex and the velocity fluctuation in the vortex breakdown flow field are illustrated as results of the precession on the vortex core section, analogous to the precession of a solid body with a fixed point. The frequency of the velocity fluctuation is demonstrated experimentally and theoretically to be proportional to U0/L. Secondly, a modification, accounting for turbulence, of Hall’s method of numerical calculation is described. The concept of eddy viscosity is introduced, and the fundamental system of the theory consists of a set of quasi-two dimensional equations which are to be solved numerically. Calculation is actually carried out in the case of a flat-plate delta wing model with an apex angle of 50deg and an attack angle of 17deg, with initial and boundary conditions specified in accordance with the measured values. Comparison is made between the numerical and experimental results, showing good agreement between them, when the chosen value of eddy viscosity is 4 to 5 times larger than the kinematic viscosity.
資料番号: NALTR0423000
レポート番号: NAL TR-423
連携機関・データベース国立情報学研究所 : 学術機関リポジトリデータベース（IRDB）（機関リポジトリ）
提供元機関・データベース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