实测了导流型人工鱼礁体在纵向布设间距1.0L(L为礁体长度)和2.0L下的流场及受力特性,计算了导流型人工鱼礁体在横向布设间距(0.5L、1.0L、1.5L、2.0L)及纵向间距(0.5L、1.0L、2.0L、3.0L、4.0L、5.0L)下的水动力特性,研究结果表明:导流型人工鱼礁体流速及阻力系数的计算值与实测值吻合较好; 横向布设下上升流高度、阻力系数均与布设间距成反比,0.5L时,上升流高度较大,1.0L时,上升流体积较大; 纵向布设下上升流高度较平稳,上升流水平跨度、上升流体积与布设间距成正比,大于4.0L时,趋于平缓,4.0L时,流场效应较好.通过上述不同纵横间距比的组合优化研究,可在工程中为人工鱼礁体选型、设计和布设提供参考.
Objective: In recent years, renewable fisher resources have declined. The use of artificial reefs can promote the development of fisheries. Artificial reef is regarded as a marine engineering structure for improvement and restoration of ecological environment in natural water. Artificial reefs secure the potential to attract and aggregate fish to enhance their supplies. In this article, the hydrodynamics of artificial reefs with different distances between adjacent reefs is investigated. Hopefully, this work will provide a scientific basis for the structure design of artificial reef.
Methods: The hydrodynamics of the artificial reefs is analyzed primarily by means of computational fluid dynamics (CFD). For the purpose of validating simulation accuracies, the test experiment, in which the same material and environment condition are used, is operated in a channel. Also, the polymethyl methacrylate is chosen as the artificial reef material with the model scale = 20. Results show that the simulation agrees satisfactorily with the experiment. The continuity equation and the Reynolds-averaged Navier-Stokes equations in Cartesian coordinates for incompressible flows are used.
Results: The velocity of the artificial reef and the force exerted on the reef at the distance of 1.0L and 2.0L in the flow direction are measured. Hydrodynamic parameters of the artificial reef at the distance of 0.5L, 1.0L, 1.5L and 2.0L in the vertical direction and the distance of 0.5L, 1.0L, 2.0L, 3.0L, 4.0L and 5.0L in the flow direction are computed. It is found that velocities and drag coefficients of simulations and experiments agree with each other satisfactorily. When the artificial reef is placed in the vertical direction, the height of upwelling and the drag coefficient decrease with the increase of the distance. When the distance reaches 0.5L, the height of upwelling becomes the largest, and when the distance reaches 1.0L, the volume of upwelling becomes the largest. By contrast, when the artificial reef is placed in the flow direction, the height of upwelling varies only slightly, whereas the horizontal span of upwelling and the volume of upwelling increase with the increase of the distance. When the distance reaches 4.0L, the increase speed is small, and the flow field effect is best
Conclusions: The arrangement of artificial reef exerts a significant influence on the flow field, and also affects the ecological function, such as the aggregation of fish and the attachment of algae among others. The distance in transverse and longitudinal directions between adjacent reefs is critically related to very common structure designs for artificial reefs. In this article, flow-field scopes of reefs with different arranges are investigated using the CFD method. The reef arrangement fundamentally changes the velocity and the direction of the flow passing through the reef, and plays a decisive role in enhancing the flow field scope. It is suggested that 0.5L (L = the length of the reef) in the transverse direction and a value smaller than 4.0L in the longitudinal direction yield the minimal drag coefficient.
