Study on Shock Flutter in Transonic Cascade

Research Project

Project/Area Number	60460100
Research Category	Grant-in-Aid for General Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	Fluid engineering
Research Institution	University of Tokyo
Principal Investigator	TANIDA Yoshimichi Faculty of Engineering, University of Tokyo, 工学部, 教授 (50013628)
Co-Investigator(Kenkyū-buntansha)	SHIRATRI Toshimasa Tokyo Metropolitan Institute of Technology, 助教授 (10107162) NAGASHIMA Toshio Faculty of Engineering, University of Tokyo, 工学部, 助教授 (70114593)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥2,300,000 (Direct Cost: ¥2,300,000) Fiscal Year 1986: ¥2,300,000 (Direct Cost: ¥2,300,000)
Keywords	Transonic Flow / Cascade / Shock Wave / フラッタ
Research Abstract	In a transonic cascade, the shock-stall flutter is presumed to occur, which brings about a violent blade vibration, leading to the blade failure. In order to elucidate the effects of the shock behaviour on the blade characteristics, an experiment was first carried out on the cascade with no stagger, in which the blade oscillates out of phase with each other. The measurement of the flutuating pressure distribution on the blade shows that the shock oscillates behind the blade oscillation with a constant time-lag, leading to the possibility of shock flutter in the range of a higher blade frequency. During the above experiment, the self-excited oscillation of shock was observed, which preu-mably brings about the most violent blade vibration when both frequencies coincide. For making clear the mechanism of the self-excited oscillation of shock, the fluctuating shock location was detected by the newly developed optical system, while the unsteady pressure distribution in the flow behind the shock was also measured. The results show that the self-excited oscillation of shock is caused by the propagation of the pressure fluctuation between the shock, which is generated by the shock-boundary layer interaction. The theoretical approach has also been carried on. First, with the assumption of relaxed Kutta condition at the blade trailing edge, the one-dimensional analysis gives the frequency of the self-excited shock oscillation in good agreement with the experimental ones. Further, for the shock-stall flutter in the two-dimensional cascade, the analyses by the Finite Element Method and the Finite Difference Method are both in progress.