| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent generation of an air suction vortex with simple structure, without carrying out civil engineering works for vortex prevention. SOLUTION: A subpassage forming member 28 for forming a subpassage 30 between the subpassage forming member 28 and an outer peripheral surface of the suction part 14 is approximately concentrically arranged on an outer periphery of the suction part 14 having a suction opening 14a arranged to an open channel.</p> |
