中层取水是防止钉螺通过涵闸引水扩散的主要工程措施之一，在长江流域血吸虫病疫区得到了较广泛的应用；但在实际应用过程中存在着一定的问题。影响阻螺效率的主要问题是取水口容易形成漩涡，吸入水体表面漂浮物，从而带进钉螺。应用理论分析和概化模型试验对取水口漩涡形成机理和特征及消涡措施进行了研究，提出了简单易行有效的消涡措施。研究结果表明：漩涡发生在取水口上方与垂直方向夹角30度的区域，横向消涡梁是一种简单易行有效的消涡措施。

The middle layer water intake is one of main engineering measures for intercepting oncomelania snails, and it is a key structure for preventing snails dispersion through sluice gates. The middle layer water intake structure for oncomelania snails subsists some problems in practice. For example, snails with floating debrises will be absorbed into pipe by vertical-axis vortex. So the flume test was done to study the formation mechanism of the vertical-axis vortex and vortex elimination measures. The simple and effective measures to eliminate vortex have been suggested. The study results show that there exists the vortex in the upper water area with an angle 30 degree against vertical direction, and a cross beam set in the water area is an effective measure for eliminating vortex of the water intake.