Efficient placement models of labyrinth-type artificial concrete reefs according to wake volume estimation to support natural submerged aquatic vegetation

The present study presents efficient placement models of labyrinth-type artificial concrete reefs (LT-ACRs) to support natural submerged aquatic vegetation beds or enhance macrophyte beds [Undaria pinnatifida (Harv.) Suringar, Laminaria sp., Ecklonia stolonifera Okamura, and Sargassum fulvellum (Turner) C. Agardh] in the coastal waters of South Korea. To reach an efficient solution, wake regions were obtained for 12 LT-ACR placement models using the element-based finite volume method and wake volume concept. The optimal flatly distributed placement models were identified in intervals between neighboring reefs (i.e., longitudinal width: 1 m ≤ W1 ≤ 3 m; transverse width: W2 = 5 m), which resulted in wake volumes of 43.8, 38.5, and 39.5 m³. The optimal models are regarded as more efficient than the maximum wake volume case because their geometries sustain the intervals between neighboring reefs. Overall, labyrinth-type artificial concrete reefs are efficient because they have relatively wide surfaces and small drag coefficients, and their optimal placement models satisfy Korean practices, which dictate that the intervals should not exceed 5 m. However, the hydrodynamic and economic pros and cons of intervals >5 m were not assessed in the present study.