This work investigated the self-cleaning performance of three drain modes in circular bottom drain water tanks with tangential inlet. Removal experiments in center, eccentric and center-eccentric combined (dual) drain modes were carried out in a miniature tank with a diameter of 0.44 m and a depth of 0.215 m for a hydraulic retention time of 30 min using two artificial bio-wastes mimicking fish fecal and uneaten feed matters. The experiments were simulated by using the Eulerian model of FLUENT. The correlations between the numerical solutions and the experimental data confirm the adequate reproduction of the bio-waste removal behavior. It was confirmed that the self-cleaning performance of the center drain is four times greater than that of the eccentric drain under the same water supply condition. Since the water drainage speeds of the dual-drain were less than those of the other two drains under the same water supply condition, the order of precedence for self-cleaning performance was the center drain, dual-drain, and eccentric drain. According to numerical experiments in the full-size tank with a diameter of 9.15 m and a depth of 1.83 m for hydraulic retention times of 30 and 55 min, the above order was kept constant, but the self-cleaning performance of the center drain was reduced by 1.04 times of that in the eccentric drain. The numerical experiments of all possible dual, triple and quadruple bottom drain modes in the full-size tank with one center drain and three eccentric drains showed that an increase of the eccentric drains causes a decrease of the drainage speed and thus does not lead to a noticeable improvement in self-cleaning performance. Numerical experiments in a medium-size tank showed that the above order was also kept constant. The reason why the self-cleaning performance of the center-eccentric combined drain is lower than that of the center drain is that its reduced drainage speed does not have kinetic energy enough to push the bio-wastes up to the height of the outlet. The center drain has the best self-cleaning performance in the circular tanks with tangential inlet and if the drainage speed is not sufficiently increased, the multiple drain system might have negative effect on self-cleaning performance.

这项工作调查了切向入口的圆形底部排水水箱中三种排水模式的自清洁性能。在直径为 0.44 m、深度为 0.215 m、水力停留时间为 30 分钟的微型水槽中，使用两种模拟生物废弃物进行了中心、偏心和中心-偏心组合（双）排水模式的去除实验鱼粪便和未食用的饲料物质。实验采用FLUENT的欧拉模型进行模拟。数值解和实验数据之间的相关性证实了生物废物去除行为的充分再现。经证实，在相同供水条件下，中心排水管的自洁性能是偏心排水管的四倍。由于在相同供水条件下，双排水器的排水速度小于其他两种排水器，因此自清洁性能的优先顺序为中心排水器、双排水器和偏心排水器。根据在直径为 9.15 m、深度为 1.83 m、水力停留时间为 30 和 55 min 的全尺寸水箱中进行的数值实验，上述顺序保持不变，但中心排水管的自清洁性能为比偏心排水管减少1.04倍。所有可能对偶的数值实验，在具有一个中心排水管和三个偏心排水管的全尺寸罐中的三重和四重底部排水模式表明，增加偏心排水管会导致排水速度降低，因此不会导致自清洁性能的显着改善。在中型水箱中进行的数值实验表明，上述顺序也保持不变。偏心组合式排水器的自洁性能之所以低于中心式排水器，是因为其降低的排水速度没有足够的动能将生物垃圾推到出水口的高度。中心排水在切向进水的圆形水箱中自洁性能最好，如果排水速度不够快，