The Fibre Optic Three-Dimensional Laser-Two-Focus Velocimeter for the Low-Speed Windtunnel Part I Two- Dimensional Measurement Evaluations

A fibre optic three-dimensional Laser-Two-Focus(L2F)-Velocimeter was introduced in the Aircraft Aerodynamics Division in 1988. The former half of the present report describes both an outline and the principle of this system for two-dimensional measurements. In the latter half, the L2F-Velocimeter is evaluated by using three types of flows, i.e., two-dimensional wake, three-dimensional boundary layer and quasi two-dimensional free jet with, and occasionally without, seeding particles. Furthermore, several seeding particles such as paraffine vapor, mosquito-repellent smoke and tobacco smoke are used for evaluations. The axial velocity component from the L2F-Velocimeter is pointwisely compared with a calibrated velocity. The comparison is extended to the transverse mean velocity component/fluctuating components with hot-wire measurements, in which great care was taken with the linearity and wire inclination. There is no incongruity in comparison except in low turbulence with less than 2％ intensity to the lal velocity .In summary, features of the fiber optic L2F-Velocimeter are its applicability to natural seed, wall-proximity and non-calibration measurements, although it is apriori known that the L2F-Velocimeter is not adaptable to both reverse flow and high turbulence measurements.
資料番号: NALTM0627000
レポート番号: NAL TM-627