Experimental Study on Flow Structure Induced by a Porous Box-type Artificial Reef

Artificial reefs are common auxiliary structures in coastal engineering. In this study, a flume experiment is conducted to study on the flow structure inside and outside a porous box-type artificial reef by means of ultrasonic probes and Particle Image Velocimetry (PIV). The influence of the reef on water level and flow fields in vertical and horizontal directions were analyzed. The results show that: 1) the water level on two sides of reef gradually decreases and water level over the reef changes greatly along the course, which indicates the reef can reform the flow regime; 2) in vertical flow field, several pairs of vortices are generated inside the reef due to the interaction between inflow current from the stoss face holes and backflow behind the reef, and the outflow current through the reef crest holes enhances the water exchange over the crest; 3) in horizontal flow fields, a pair of wake vortices formed behind the reef strengthen the water exchange between inside and outside the reef, and the near crest flow field generates more and larger vortices with weaker velocity than that in the near bottom flow field owing to more energy dissipation. The study reveals the flow structure characteristics and exchange mechanism of current inside and outside the reef, which provides a scientific guidance for optimizing the reef design and effectively controlling the reef-induced flow field.