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The initial artificial oyster reef (AOR) model. A total of 48 initial AOR models were con- structed by considering four shell orientations, six compositions, and two shell penetration depths.
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Oyster reefs are currently at risk of severe decline due to dangerous human interference and its aftermath; hence, artificial oyster reefs (AORs) have been utilized for their restoration. AORs with high vertical reliefs interact with the surrounding flow, constitute a reverse flow, and create a wake region in which concentrated nutrients and food o...
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... therefore first constructed an initial AOR model by fixing the shells to a flat substrate of 0.3 m (length) × 0.3 m (width) × 0.05 m (height) (Figure 2). We then considered four shell orientations such as convex, concave, mixed 1, and mixed 2 and six compositions such as 3 × 1, 3 × 3, 3 × 5, 5 × 1, 5 × 3, and 5 × 5 ( Figure 2); here, the first and second numbers indicate the number of oyster shells perpendicular to and parallel to the inlet flow direction, respectively (Table 1). Moreover, we considered two shell penetration depths of 10% and 50%; hence, the 48 initial AOR models were designed as illustrated in Figure 2. J. Mar. ...Citations
... Structural complexity may be one of the variables aiding in the design process, and the calculation of the complexity index (SI) is proposed in this study. According to the formulations proposed by [93], the SI index is computed according to Equation (1): ...
... Parametric design is particularly useful for iteratively computing the total surface of the MFAR A t using a single operation, as well as further optimization. On the other hand, the bottom projection area A b represents the rectangular area occupied by the MFAR, as suggested by [93,94], obtained by the vertical projection at the base plane. In the present research, the vertical projection of the 3D shape at the base plane of the entire MFAR structure is a complex shape (see Figure 15); therefore, A b is proposed to represent this projection on the base plane, as shown in the red shape in Figure 15. ...
... The results shown in Table 2 suggest that, by using the parametric design and applying a relatively simple surface refinement on the initial MFAR, the outcome can lead to a significant increase in SI values, reaching up to a 21.6% difference for case 4 when compared to the reference design (case 1). As demonstrated by [93], the SI tends to be linearly proportional to the wake volume created behind the MFAR in the water flow for ARs with After the surface refinement with spherical objects was applied to all four cases, the following geometrical parameters were derived: total surface area A t , bottom projection area A b , complexity index ϕ s , as well as total structure volume. The "ϕ s difference" and "volume difference" rows provide the difference of results between the reference case (case 1) and each of the other surface refinement variations (cases 2 to 4), respectively. ...
Artificial reefs featuring different shapes and functions have been deployed around the world, causing impacts on marine ecosystems. However, the approaches typically used to deliver topological complexity, flexibility and expanding requirements to prospective structures during the initial design stages are not well established. The aim of this study was to highlight the advantages and provide evidence on how modularity and parametric design can holistically leverage the performance of multifunctional artificial reefs (MFARs). In particular, the goal was to develop a parametric design for MFAR and establish a direct relationship between specific design parameters and the MFAR target functions or design requirements. The idea of implementing the parametric design for generating the initial biomimetic geometry of the individual modular unit was explored. Furthermore, possible ways of manipulating the geometric parameters of the individual module and the whole assembly were proposed. The findings suggest that, by adopting the developed procedure and the examples studied, several functions may be reached within a single assembly: the promotion of marine biodiversity restoration, the support of scientific platforms with various sensors, as well as the development of recreational diving and of touristic attraction areas. Acquired knowledge suggests that the concept of a nature-like design approach was developed for artificial reefs with varying scales, complexity and functions, which widens the range of possibilities of how smart design of human-made underwater structures may contribute to benefiting the near shore ecosystems.
... These studies primarily considered the static or initial state of oyster reefs, with little known about the interaction between their hydrodynamic characteristics and the growth process of restored oyster reefs. Recently, Kim et al. 28 developed a set of artificial oyster reef models comprising different numbers of shells. They analyzed correlations between structural characteristics and wake regions using the elementbased finite volume method. ...
... The recruitment stages were modeled by increasing the shell length and adjusting the number of living oysters per mat, with RS ¼ 1-5 representing approximately 1-4 years postrestoration, respectively. The reef models are designed to overcome the limitations of previous models by Kim et al. 28 and to simulate the random development process, such as the growth of spat. Specifically, reefs with older restoration ages are characterized by more complex canopy structures, like sharp edges and branches. ...
Oyster reefs play a dual role in the ecological and economic sustainability of global estuarine resources. Due to human activity and climate change, the prevalence of cosmopolitan oyster reefs has noticeably declined in recent decades, triggering a global restoration movement. However, the hydrodynamic functions of oyster reefs during and after restoration, particularly the impacts of growth and morphology on the flow field, remain poorly understood. This study employs the lattice Boltzmann method coupled with large-eddy simulation to simulate unidirectional flow around restored oyster reef models using the open-source Palabos library. It examines the effects of unidirectional flow velocity and reef morphology on hydrodynamic characteristics. The research analyzes spatial and temporal variations in velocity, vorticity, and turbulence structure around the reef. The findings indicated significant flow field differences between the initially restored reefs and those post-restoration. The dimensionless wake region scale parameters of the initially restored reefs exhibit hysteresis effects, generating larger turbulence during the post-recruitment stage than in the initial stage. Areas of high turbulence in the wake are associated with above-canopy flow, bypass flow, and within-canopy flow. The presence of gaps and branches in the reef leads to complex turbulence structures and irregular vortex shedding in the reef's wake at the post-recruitment stage. These results are valuable for assessing oyster reef resilience and planning effective restoration interventions.
In recent decades, exogenous pressures have contributed to habitat loss and fragmentation of oysters, resulting in a growing interest in restoring oyster reefs. Hydrodynamics of oyster reefs control processes such as oyster growth and survival, nutrient cycling, and sediment transport, which are key considerations in evaluating and optimizing oyster reef restoration interventions. A systematic literature review was conducted to summarize and analyze the present research and trends in oyster-reef hydrodynamics. The finding reveals that 67.5% of the reviewed studies focused on field tests and laboratory experiments, while 30% explored numerical modeling and machine learning methods. The meta-analysis results show that the mean wave transmission coefficients of submerged oyster reefs are greater than those of emergent ones. Shell-based reefs and the assemblage of constructed oyster reefs and vegetation offer wave attenuation benefits second only to those of natural oyster reefs. The local hydrodynamics of oyster reefs are influenced by hydrological regime, reef design, placement, and biological change. In particular, a synopsis of common measuring methods and reef roughness metrics is included, along with major challenges and suggestions for future studies.
