| 摘要 |
A device (10) and method for inducing a longitudinal force into a filament (14) are disclosed. The device includes an enclosure (16) that defines a chamber (18) having a first orifice (32) and a second orifice (42) located in respective opposing end walls. The filament extends through the first orifice, chamber and second orifice. The area of the first orifice is slightly larger than the transverse cross-sectional area of the filament, and the area of the second orifice is larger than the area of the first orifice. The chamber is filled with a pressurized fluid (12), which flows out of the enclosure through the first and second orifices, creating corresponding drag forces (56, 58) on the filament that are in opposite directions to one another. Due to the cross-sectional area of the second orifice being larger than the cross-sectional area of the first orifice, the drag force created by the fluid flowing out of the second orifice is larger than the drag force created by the fluid flowing out of the first orifice, thereby creating a net drag force (15) in the direction of flow through the second orifice. The net drag force induces a longitudinal force into the filament.
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