噴流撹乱を用いた円管内助走部後段における孤立乱流塊の特性

抄録

The laminar-turbulent transition of a boundary layer induced by a jet injection in the inlet region of a circular pipe was experimentally investigated. The jet was periodically injected radially from a small hole in the inlet region into the pipe flow. The turbulence induced by the jet within the boundary layer developed into turbulent patches which then grew in the axial, circumferential and radial directions downstream. A single hot-wire probe was used in the measurements. The axial velocity component was measured at four downstream stations, one within the inlet region and the other within the development region. Output voltage of the hot-wire was digitized and data was processed by a PC. An ensemble-averaging based on the signal from the jet trigger was performed. Mean and fluctuating velocity in the axial direction and intermittency factor which is the fraction of turbulence were obtained.