挡潮闸矩形孔口式鱼道紊流结构及放鱼试验研究

对挡潮闸枢纽中矩形中孔、底孔鱼道中紊流结构进行了较为系统的试验研究,并做了放鱼试验。选择了一种鱼类偏爱流速所对应的流量作为典型流量,考虑了不同的孔口位置(中孔和底孔),用声学多普勒测速仪(ADV)量测了测点的三维瞬时流速及流向,分析了矩形孔口鱼道的三维时均流速分布特征、断面最大流速沿程变化规律、流速矢量场、紊动强度分布及雷诺应力分布。此外,还通过放鱼试验,利用在鱼体植入T形标签和高速摄影机观察了过鱼对象对中孔、底孔的反应情况,分析了过鱼对象与矩形孔口鱼道紊流结构的关系。试验结果表明:水流经中孔形成三维紊动自由射流,经底孔形成三维壁面射流,中孔纵向流速呈高斯分布,而底孔纵向流速则近似为高斯分布,流速由孔口向两侧逐渐减小;中孔和底孔横向流速在位于孔口范围内的纵剖面上沿程减小,孔口之外则变化较小;中孔和底孔垂向流速分布特征表现为在铅垂方向上均存在旋涡;在中孔水平面和纵剖面上,纵向最大流速均沿程衰减;中孔和底孔情形孔口处紊动强度和雷诺应力比非孔口处大得多,而非孔口处不同水深平面上紊动强度和雷诺应力变化趋于平缓;过鱼对象喜爱在紊动强度分布的峰值区和雷诺应力较大变幅区溯游。

An experimental study of turbulent structure and fish test in a rectangular orifice fishway of tidal sluice

Turbulent structures and fish tests in rectangular central and bottom-orifice fishways of a tidal sluice complex were experimentally studied. A typical flow rate corresponding to the preference velocity of fish was selected. Different orifice locations (central and bottom orifices) were considered. Three-dimensional instantaneous velocity and flow direction at each measuring point were measured by Acoustic Doppler Velocimeter (ADV). Three-dimensional time-averaged velocity distributions, decay of the maximum velocity along flow direction, velocity vectors, turbulence intensity distributions and Reynolds stress distributions on different planes of flow depth and different longitudinal profiles in the pool of rectangular orifice fishway were analyzed. In addition, the swimming behaviors of target fish in the fishway were observed by high speed photography based on the fish tests with implanted T-shaped tag. The relation between target fish and turbulent structures in the rectangular orifice fishway was analyzed. The experimental results showed that the three-dimensional turbulent free jet and wall jet were formed after flowing past central and bottom orifices, respectively. The longitudinal velocity for the central orifice exhibited Gaussian distribution, whereas the velocity for the bottom orifice showed approximately Gaussian distribution, and the velocity gradually reduced from the orifice centerline to the sides; the transverse velocity within the orifice for the central and bottom orifices decayed along flow direction, and the velocity changed slightly outside the orifice; the vertical velocity distribution for the central and bottom orifices exhibited occurrences of vertical vortex; on the horizontal and longitudinal planes, the maximum longitudinal velocity decayed along flow direction. In the case of central and bottom orifices, the turbulence intensity and Reynolds stress within the orifice were much larger than those outside the orifice. And variations in the turbulence intensity and Reynolds stress on different depth planes outside the orifice tended to be mild. The target fish preferred swimming in the peak-value range of turbulence intensity and the larger amplitude range of variation in Reynolds stress.