钉螺水体沉降实验研究

在玻璃筒和玻璃水槽中模拟不同流速水体,对各期钉螺作水体沉降试验,钉螺在静水中呈水面漂浮和水中沉降两种状态;在动水中呈水表漂流、水中沉降悬移、水底推移滚动和扬起悬移等4种运动状态.钉螺在水中沉速与钉螺大小、水温高低呈正相关;钉螺沉降轨迹角度与水流速度呈正相关,与钉螺大小呈负相关.钉螺沉降水平悬移平均速度接近平均水流速度.用所测各期钉螺的平均沉速推算不同深度和不同流速水体的钉螺沉降悬移距离,与实测平均悬移距离无明显差异.最小钉螺的最低起动流速在8—16cm/s之间,最低扬动流速在24—32cm/s之间.

EXPERIMENTAL RESEARCH ON SNAIL SETTLING IN WATER

Snail settling experiments of different snail stages in glass cylinds and glass trough with circulating water of different velocities were carried out. The results were as follows :In static water,snails were either drifting or settling;in current water,4 moving states were seen,ie, drifting,suspended settling,rolling at trough bottom and saltatory suspending near bottom. The settling velocity of snails in water were positively correlated with snail size and water temperature. The angle formed by water level and track suspended settling of snail had positive correlation with water velocity and negative with snail size. The average suspending velocity was close to the average current velocity and the calculated suspended distances at different water depth and current velocity showed only slight difference in comparing with the measured ones. It was also found (according to the experiments) that the lowest water velocity for snail to start off at bottom was within 8 ?6cm/s,and the lowest velocity for saltatory suspending of snail at bottom was within 24 ?2cm/s.