| 摘要 |
The invention relates to apparatus for making waves in a liquid in test tanks and the like by the back and forth movement in the liquid of a displacer. A problem caused by the escape of liquid round the side of the displacer during such movement is overcome by the provision of a seal between the displacer and the wall of the tank, which seal by a rolling action allows relative movement between the wall and the displacer.
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