Effect of flow deflectors on local scour around artificial reefs under steady current: Experimental and numerical investigations

• The combination of flume experiments and CFD simulations provided a comprehensive analysis of both scour development and the effect of different deflector configurations on flow patterns and shear stress distribution. • The optimized deflector design (AR11) reduced the maximum scour depth by 46 %, providing an effective countermeasure against local scour and improving the stability of the reef. • Detailed analysis provided critical insights into the interplay between flow patterns, shear stress, and scour, demonstrating the benefits of deflector-enhanced reef designs. • The deflector effectively altered flow patterns, reduced shear stress, and mitigated upstream scour, ensuring structural stability and a suitable habitat for marine life. Artificial reefs are submerged structures used to rehabilitate marine ecosystems and restore fishery resources. Field investigations have revealed that local scour poses a significant threat to these structures in various regions. Despite this, there is limited research on scour countermeasures for artificial reefs and a lack of understanding regarding the flow patterns that influence scour. This study examines the effects of different deflectors on scour depth and flow patterns around artificial reefs, focusing on a control model (AR1) and an optimized model (AR11). The experiments were conducted under steady, unidirectional current conditions. Flume experiments demonstrated that AR11 reduced the maximum scour depth by approximately 46 % compared to AR1 and effectively prevented reef tilting. Flow fields on the scour bed of AR1 and AR11 were reconstructed using hydrodynamic modelling of scour topography and computational fluid dynamics (CFD). The analysis revealed that the main flow features affecting the scour around AR1 were a counterclockwise vortex on its side and a vortex within the scour hole. In contrast, AR11 effectively mitigated the adverse effects of these vortices, thereby reducing scour around the artificial reef.