沼蛤幼虫管道湍流灭杀试验研究Ⅰ:水力学特征

Experimental study on the effect of pipeline turbulence on killing Limnoperna fortunei larvae I. Hydraulic characteristics

沼蛤(Limnoperna fortunei)是贻贝科软体动物,可在管道造成生物污损和堵塞。沼蛤以浮游幼虫形态随水流入侵管道,其幼虫死亡率在高频脉动作用下明显提高。为寻找控制沼蛤入侵管道的有效途径,本研究选取3种孔板和3种筛网采用50 cm和25 cm两种间隔布置在试验管道中制造紊动,利用多普勒声学流速仪(ADV)测量其下游流场、紊动场和能谱特征等水力特性。结果发现致紊材料下游流速均出现短暂波动。大孔径孔板下游横向流速波动增强,加密布置可抑制此波动。筛网的阻水效应很小,加密布置可提高水流过筛流速。孔板下游紊动强度分布呈明显带状特征,筛网则不如孔板均匀,两者下游紊动强度均沿程降低。在下游5 cm距离内,孔板可大幅提高高频脉动能量,进而提升下游紊动强度,减小紊动长度尺度。筛网下游高频脉动能量提升幅度较小,同时低频脉动能量减弱。单级筛网比孔板消耗的水头小,加密布置并不增大单级致紊材料消耗的水头。综合来看,6 mm孔板、10 mm孔板和3 mm筛网具有较高管道湍流灭杀沼蛤幼虫的潜力。

Golden mussel（Limnoperna fortunei）, belonging in the family Mytilidae, can lead to biofoulingand pipe clogging. The species invades the pipelines during its planktonic larva stage, which is apt to bekilled by high frequency turbulence. To obtain efficient methods to prevent golden mussel invasion in thepipelines,3 types of galvanized plates embedded with circular pores and 3 types of galvanized wire mesheswere selected as turbulence-generating materials（TGMs） and installed in an experimental pipe（averageflow velocity≈1 m/s） with intervals of 50 cm and 25 cm. The downstream flow field of the TGMs was mea-sured by Acoustic Doppler Velocimeter（ADV）. The experimental results indicated that the velocity distribu-tion was disturbed by the TGMs in short longitudinal distance. Velocity disturbance was observed in thedownstream transverse sections of the 6 mm and 10 mm pore plates and was weakened with the TGM inter-val reduced from 50 cm to 25 cm. All the wire meshes exhibited little influence on discharge capacity ofthe pipe and might accelerate downstream flow velocity within short distance if the wire meshes were dense-ly installed. The downstream turbulence intensity of the pore plates showed a banded distribution patternwhile the wire meshes had a less distinct banded pattern. The downstream turbulence intensity of theTGMs turned to decline until the next installation. The energy of high frequency turbulence behind thepore plates were enhanced to a large extent. Meanwhile,the turbulence intensity was improved and the ed-dy length scale was reduced in a range of 5 cm downstream the materials,which was beneficial in goldenmussel larvae killing. The wire meshes presented a much weaker effect on increasing the high frequency tur-bulence energy and led an energy decrease of low frequency turbulence. The installation of pore plates re-sulted in larger resistance than wire meshes and dense layout did not lead to higher resistance for eachTGM. In summary,6 and 10 mm pore plates and 3 mm wire mesh revealed higher potential for improvingthe effect of pipeline turbulence on killing Limnoperna fortunei larvae.