| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for removing sludge in a rearing water tank for fishes designed to gather the sludge such as fish feces precipitating in the bottom of the water tank by actions of a fluid during draining and effectively discharge the sludge. SOLUTION: The water tank 1 is formed by installing a large-diameter part 1a and a small-diameter part 1b so that the diameter D2 of the cylindrical lower part is smaller than the diameter D1 in the upper part and dividing the parts through a net body or a lattice body 11. A drain 2 and a discharge pipe 3 having a diameter comparable to that of the drain 2 are mounted in the bottom of the water tank with a somewhat gap S kept from the bottom of the water tank. When water is periodically discharged from the drain 2, a swirling flow is imparted to water in the upper part 1a of the water tank. When discharged from the drain 2 in the bottom, water is moved to the lower part 1b of the water tank. Since the diameter D2 of the lower part 1b of the water tank is smaller than the diameter D1 of the upper part of the water tank, the swirling speed is increased by the law of preservation of angular momentum. On the other hand, the swirling speed is extremely reduced due to the viscosity of water in the bottom of the water tank 1. Thereby, centrifugal force by swirling is smaller than that of water in the upper part. A strong flow toward the center is produced in the bottom because of the imbalance and the flow is bent upward in the center of the swirling. COPYRIGHT: (C)2006,JPO&NCIPI
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