Limiting downstream dispersal of invasive carp egg surrogates using a laboratory-scale oblique bubble screen

We conceptualize and test a non-intrusive barrier, comprised of an oblique bubble screen (OBS) oriented at an angle to the mean flow, to prevent the downstream dispersal of invasive carp egg surrogates. Three surrogates of different densities and diameters were tested. Secondary flows created by the OBS were tuned to redirect surrogate eggs to facilitate their capture. Surface particle image velocimetry and acoustic Doppler velocimetry were used to characterize secondary flows. We assessed the influence of airflow rate, OBS angle, mean flow velocity, and surrogate density on particle redirection. In general, redirection efficiency improves by increasing the OBS angle with respect to the cross-section. At a mean flow velocity of 0.75 metres per second (m/s), the OBS system redirected up to 60% (%) of positively buoyant particles (specific gravity SG = 0.9, and diameter d = 7.09 millimetres [mm]) and 40% of semi-buoyant particles (SG = 1.001, d = 3.1 mm). Negatively buoyant particles (SG = 1.04, and d = 5.90 mm) were redirected by the physical structure of the diffuser rather than by OBS-induced flow. The study shows that an OBS system can be used to effectively redirect carp-egg surrogates over a wide range of particle sizes and densities, allowing for selective targeting of undesired particles in streams.本研究构思并测试了一种非侵入式阻控装置：该装置由与主体流呈一定夹角布设的斜向气泡幕（oblique bubble screen, OBS）构成，用于阻止入侵性鲤鱼卵替代物向下游扩散。本研究共测试了三种不同密度与粒径的替代物。斜向气泡幕诱导产生的二次流可被调控，用于对鲤鱼卵替代物进行导流，以辅助其被捕获。本研究采用表面粒子图像测速法（surface particle image velocimetry）与声学多普勒测速法（acoustic Doppler velocimetry）对二次流特性进行表征。本研究评估了气流速率、斜向气泡幕夹角、主体流流速以及替代物密度对颗粒导流效果的影响。总体而言，导流效率随斜向气泡幕与过水断面夹角的增大而提升。当主体流流速为0.75米每秒（m/s）时，该斜向气泡幕系统可实现对最高60%的正浮力颗粒（比重（specific gravity, SG）=0.9，粒径d=7.09毫米[mm]）以及40%的半浮力颗粒（SG=1.001，d=3.1mm）的有效导流。而负浮力颗粒（SG=1.04，d=5.90mm）的导流则依赖扩散装置的物理结构，而非斜向气泡幕诱导产生的流场。本研究结果表明，斜向气泡幕系统可在较宽的粒径与密度范围内对鲤鱼卵替代物实现有效导流，从而可实现在河道中对非目标有害颗粒进行选择性拦截。