| 摘要 |
PCT No. PCT/NL97/00276 Sec. 371 Date Jan. 26, 1999 Sec. 102(e) Date Jan. 26, 1999 PCT Filed May 16, 1997 PCT Pub. No. WO97/44674 PCT Pub. Date Nov. 27, 1997In order to determine the flow status of a surface moving through the fluid, it is proposed to mount flaps on that surface. Such flaps hinge from the one to the other position depending on the flow conditions. The position of such flaps can be rendered particularly readily visible if the one side of the flap has an appearance which differs from that of the other side of the flap and/or if the surface which is covered by the flap has an appearance in the one end position which differs from the appearance of the surface which is covered by the flap in the other end position. A different appearance can, for example, be realized by providing a differently colored, reflective or retroreflective surface or existing differences in transmission, fluorescence or phosphorescence or even coverage of an illuminated surface. |
