scholarly journals Numerical Analysis of the Flow Effect of the Menger-Type Artificial Reefs with Different Void Space Complexity Indices

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1040
Author(s):  
Xinxin Wang ◽  
Xianyi Liu ◽  
Yanli Tang ◽  
Fenfang Zhao ◽  
Yan Luo
Keyword(s):  
Flow Field ◽  
Fractal Theory ◽  
Velocity Ratio ◽  
Artificial Reef ◽  
Space Complexity ◽  
Artificial Reefs ◽  
Void Space ◽  
Spatial Complexity ◽  
Complexity Index ◽  
Reef Models

Based on fractal theory, a regular fractal is used to construct symmetrical reef models (e.g., cube and triangle reef models) with different fractal levels (n = 1, 2, 3). Using the concept of fractal dimension, we can better understand the spatial effectiveness of artificial reefs. The void space complexity index is defined to quantify the complexity of the internal spatial distribution of artificial reefs models under different levels. The computational fluid dynamics (CFD) flow simulation approach was used to investigate the effects of void space complexity on the flow field performances of the symmetrical artificial reef models. The upwelling convection index (Hupwelling/HAR, Vupwelling/VAR), wake recirculating index (Lwake/LAR, Vwake/VAR) and non-dimensionalized velocity ratio range were used to evaluate the efficiency of the flow field effect inside or around artificial reefs. The surface area and spatial complexity index of artificial reefs increase with increasing fractal level. The numerical simulation data shows that the Menger-type artificial reef models with a higher spatial complexity index have better flow field performances in the upwelling and wake regions. Compared to the traditional artificial reef models, the upwelling convection index (Vupwelling/VAR) and recirculating index (Vwake/VAR) of n = 3 fractal cube artificial reef increase by 37.5% and 46.8%, respectively. The efficiency indices of the upwelling region and wake region around the fractal triangle artificial reef model are 2–3 times those of the fractal cube artificial reef model when the fractal level is 3.

scholarly journals Numerical Study of Efficiency Indices to Evaluate the Effect of Layout Mode of Artificial Reef Unit on Flow Field

2021 ◽  
Vol 9 (7) ◽  
pp. 770
Author(s):  
Jiating Zhang ◽  
Lixin Zhu ◽  
Zhenlin Liang ◽  
Liyuan Sun ◽  
Zhaoyi Nie ◽  
...  
Keyword(s):  
Flow Field ◽  
Significant Influence ◽  
Field Effect ◽  
Bottom Water ◽  
Numerical Study ◽  
Global Climate ◽  
Artificial Reef ◽  
Water Layer ◽  
Artificial Reefs ◽  
Unit Form

Artificial reefs (ARs) have been widely used to restore the seabed habitat and protect biodiversity. They can effectively increase the dissolved oxygen content in the bottom water layer by their disturbing effect of upwelling and downwelling. The bottom water is prone to hypoxia in summer due to the extreme weather of the global climate and excessive biomass in some marine ranching in northern China. Therefore, how to effectively use the upwelling effect of artificial reefs to alleviate this problem is a necessary subject of research. Generally, ARs are arranged by different intervals in a unit form on the seafloor, and the flow field effect is different from that of the individual reefs. However, few studies have been focused on the effect of layout mode on the flow field of a unit reef (UR). In this paper, we selected the interval between reefs (IR) and the angle of inflow (AI) as the influencing factors to study the flow field effect of UR. The upwelling and wake regions of 64 URs were presented by the efficiency and disturbance indices related to the flow characteristics and proposed an optimal layout mode having the best performance of the upwelling effect. The results showed that the interactions among the AI, the transverse, and longitudinal IRs were significant, and the AI has a significant influence on the flow field. These indices were effective and contribute to the layout optimization of UR. The AI close to 45° has a significant influence on the flow field effect of UR.

Numerical Analysis of the Effect of an Inner Structure of a Cubic Frame Reef on Flow Field

2019 ◽  
Vol 53 (2) ◽  
pp. 83-92 ◽  
Author(s):  
Zhaoyang Jiang ◽  
Zhenlin Liang ◽  
Yanli Tang
Keyword(s):  
Flow Field ◽  
Structural Design ◽  
Field Effect ◽  
Design Method ◽  
Orthogonal Design ◽  
Artificial Reef ◽  
Decisive Role ◽  
Artificial Reefs ◽  
Remarkable Effect ◽  
Orthogonal Design Method

AbstractArtificial reefs have been deposited along the coastline of China for over 30 years. The purpose of artificial reef construction is to form a changeable and complicated flow field that can promote the water exchange of different layers and attract more fish and marine organisms, and the structure of artificial reefs plays a decisive role in these processes. However, the research on the hydrodynamic character of artificial reefs has primarily focused on improving their size or shape. The guide plate has a significant effect on the flow field effect of the cubic reef, which has been confirmed in previous studies. In this article, guide plates were extended to the interior of the cubic reef and finally form an inner structure consisting of four isosceles triangles and right triangles. The flow field effect of the inner structure is numerically simulated by the orthogonal design method. Results indicate that the inner structure creates a significant disturbance on the flow field. A crossed design of hole diameters on plates contributes to the formation of upwelling and extension of the wake region. The flux of upwelling in the different planes indicates that the flow of upwelling is strong above the upwelling reef and has a remarkable effect. This study provides a scientific reference for the structural design of artificial reefs.

scholarly journals Species-specific artificial reef models for lobster (Homarus gammarus Linnaeus 1758)

2020 ◽  
Vol 37 (1) ◽  
pp. 1-7
Author(s):  
Deniz Acarlı ◽  
Semih Kale
Keyword(s):  
Artificial Reef ◽  
Artificial Reefs ◽  
Natural Environments ◽  
Marmara Sea ◽  
Homarus Gammarus ◽  
Sea Bottom ◽  
Reef Models ◽  
Different Shapes ◽  
Species Specific ◽  
Concrete Model

The objective of this study is to determine the possible artificial reef models preferred by lobster species (Homarus gammarus Linnaeus, 1758). For this purpose, eight artificial reef models at different shapes and sizes have been designed. These models include flat, grilled, U-type, cowl, fireplace chimney brick shapes made from the materials of wood, concrete and metal. Artificial reefs were deployed at 5, 10, 20 m water depths and 500 m from the shore on the coast of Erdek Ocaklar Bay in Marmara Sea. Then, monthly monitoring was conducted and SCUBA equipment were used during underwater monitoring. The time for deploying artificial reefs on the sea bottom (effort) was 233 minutes/diver and the time spent underwater by the divers was calculated as 540 minutes/diver. As a result of the study, 32 individuals of H. gammarus were observed in/around the artificial reefs. A significant increase was observed in the number of lobsters when the temperature dropped below 14°C. However, it was determined that lobster individuals preferred only concrete artificial reef models at the depth of 20 m. In addition, it was observed that small individuals preferred 40×80 cm flat concrete model (24 individuals) and large individuals preferred U-type concrete model (8 individuals). Therefore, it has been proposed to the usage of concrete artificial reef models in order to protect and ensure the sustainability of the reared lobster stocks and to release them into these artificial reefs while introducing them to the natural environments. In this context, this study will shed light on future studies.

scholarly journals REDUCTION OF WAVE OVERTOPPING RATE BY THE USE OF ARTIFICIAL REEFS

1988 ◽  
Vol 1 (21) ◽  
pp. 23
Author(s):  
Toru Sawaragi ◽  
Ichiro Deguchi ◽  
San-Kil Park
Keyword(s):  
Wave Breaking ◽  
Artificial Reef ◽  
Numerical Procedure ◽  
Artificial Reefs ◽  
Irregular Waves ◽  
Analysis Method ◽  
Wave Analysis ◽  
Wave Overtopping ◽  
Unidirectional Flow ◽  
Individual Wave

A wave overtopping rate from a sea dike of various toe depths is formulated based on a weir model in an unidirectional flow. To evaluated the wave overtopping rate from a seadike on an artificial reef by the weir model, a numerical procedure for predicting wave transformations including the effect of forced wave breaking on the reef is constructed. After confirming the applicability of the model through experiments with regular and irregular waves, the effect of artificial reef on wave overtopping is discussed. So-called individual wave analysis method is shown to he applicable to the wave overtopping caused by irregular waves.

Dispersal of yellowtail kingfish (Seriola lalandi) from a coastal embayment following a recreational fisheries enhancement stocking program: attempts to integrate aquaculture and habitat-based initiatives

2021 ◽  
Author(s):  
Alistair Becker ◽  
Michael B Lowry ◽  
D Stewart Fielder ◽  
Matthew D Taylor
Keyword(s):  
Artificial Reef ◽  
Artificial Reefs ◽  
Recreational Fisheries ◽  
Dispersal Patterns ◽  
The North ◽  
Sea Ranching ◽  
In The Wild ◽  
Yellowtail Kingfish ◽  
Seriola Lalandi ◽  
Fisheries Enhancement

Fisheries enhancement initiatives including marine stocking and artificial reef deployments are becoming increasingly common in many parts of the world. Combining the two by releasing hatchery reared fish onto artificial reefs is used in sea-ranching operations but is an approach rarely adopted for recreational fisheries. Yellowtail kingfish (Seriola lalandi) form a valuable recreational fishery in Australia and in 2018 a pilot stocking program was initiated to enhance this fishery. Fish were released onto estuarine artificial reefs in Botany Bay to evaluate if estuarine artificial reefs are suitable release habitat for juvenile yellowtail kingfish and to monitor their dispersal patterns using acoustic telemetry and a tag-recapture program. Both approaches showed similar patterns, indicating juvenile yellowtail kingfish rapidly dispersed from the release location and can travel at least 60 km during their first weeks in the wild. Twenty percent of the acoustically tagged fish entered nearby estuaries to the north and south and tagged fish were also recaptured in these estuaries, indicating that the estuaries provide habitat for juveniles. There was little interaction between stocked fish and two large coastal artificial reefs positioned near Botany Bay. Stocked yellowtail kingfish will likely disperse rapidly from release locations which is consistent with their pelagic life history. While this may present challenges to fisheries managers, increasing release numbers to maintain stocking densities over a broader area may provide a solution. Future releases of fish on coastal natural and artificial reefs are an important next step in refining stocking practices for this species and will help further identify key juvenile habitats.

Artificial Reefs in Marseille: From Complex Natural Habitats to Concepts of Efficient Artificial Reef Design

2010 ◽  
pp. 81-82 ◽  
Author(s):  
E. Charbonnel ◽  
F. Carnus ◽  
S. Ruitton ◽  
L. Le Direac’h ◽  
J.-G. Harmelin ◽  
...  
Keyword(s):  
Artificial Reef ◽  
Artificial Reefs ◽  
Natural Habitats

Impact of artificial reefs on sediment bacterial structure and function in Bohai Bay

2019 ◽  
Vol 65 (3) ◽  
pp. 191-200 ◽  
Author(s):  
Yu Wang ◽  
Jinsheng Sun ◽  
Enjun Fang ◽  
Biao Guo ◽  
Yuanyuan Dai ◽  
...  
Keyword(s):  
Artificial Reef ◽  
Control Area ◽  
Structure And Function ◽  
Artificial Reefs ◽  
Rrna Genes ◽  
Bohai Bay ◽  
Reef Area ◽  
The Future ◽  
And Function ◽  
And Control

Artificial reefs have significantly altered ecological and environmental conditions compared with natural reefs, but how these changes affect sediment bacteria structure and function is unknown. Here, we compared the structure and function of the sediment bacterial community in the artificial reef area, the future artificial reef area, and the control area in Bohai Bay by 16S rRNA genes sequencing. Our results indicated that bacteria communities in the sediment were both taxonomically and functionally different between the reef area and control area. In the artificial reef area, the α-diversity was significantly lower, whereas the β-diversity was significantly higher. Functional genes related to chemo-heterotrophy, nitrate reduction, hydrocarbon degradation, and the human pathogens and human gut were more abundant, whereas genes related to the metabolism of sulfur compounds were less abundant in the artificial reef than in the control area. The differences in bacterial communities were primarily determined by depth in the artificial reef area, and by total organic carbon in the future reef area and control area. This study provides the first overview of molecular ecology to assess the impacts of artificial reefs on the bacteria community.

scholarly journals An Assessment of Computational Fluid Dynamics as a Tool to Aid the Design of the HCMR-Artificial-ReefsTM Diving Oasis in the Underwater Biotechnological Park of Crete

2020 ◽  
Vol 12 (12) ◽  
pp. 4847
Author(s):  
Dimitrios Androulakis ◽  
Costas Dounas ◽  
Andrew Banks ◽  
Antonios Magoulas ◽  
Dionissios Margaris
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Coastal Zone ◽  
Fish Species ◽  
Artificial Reefs ◽  
Conservation Strategy ◽  
Design Improvement ◽  
Recreational Diving ◽  
Natural Reefs

Since recreational diving activities have increased in recent decades, resulting in additional environmental pressure on the coastal zone, the deployment of artificial reefs as a conservation strategy to divert mass ecotourism from fragile natural reefs has been proposed and realized in many areas of the world. Twelve units of a patented naturoid artificial reef technology developed by the Hellenic Centre for Marine Research (HCMR) were deployed in 2015 in the Underwater Biotechnological Park of Crete (UBPC) in order to create an experimental diving oasis and investigate the potential of achieving this aim for the over-exploited coastal ecosystems of this part of the Eastern Mediterranean. Assessment of the degree of establishment of artificial reefs and their ability to mimic natural ecosystems is often monitored through biological surveys and sampling. The measurement of the chemical, physical, and hydrodynamic characteristics of the water mass surrounding artificial reefs is also essential to fully understand their comparison to natural reefs. In particular, the flow field around reefs has been shown to be one of the most important physical factors in determining suitable conditions for the establishment of a number of key species on reef habitats. However, the combination of biological establishment monitoring and realistic flow-field simulation using computational fluid dynamics as a tool to aid in the design improvement of already existing reef installations has not been fully investigated in previous work. They are often reported separately as either ecological or engineering studies. Therefore, this study examined a full-scale numerical simulation of the field flow around individual already installed naturoid reef shapes, and part of their present arrangement on the sea bottom of the UPBC combined with the field-testing of the functionality of the installed artificial reefs concerning fish species aggregation. The results show that the simulated flow characteristics around the HCMR diving oasis artificial reefs were in good general agreement with the results of former studies, both for flows around a single deployed unit and for flows around a cluster of more than one unit. The results also gave good indications of the performance of individual reef units concerning key desirable characteristics such as downstream shadowing and sediment/nutrient upwelling and resuspension. In particular, they confirmed extended low flow levels (less than 0.3 m/s) and in some cases double vortexes on the downstream side of reef units where observed colonization and habitation of some key fish species had taken place. They also showed how the present distribution of units could be optimized to perform better as an integrated reef cluster. The use of computational fluid dynamics, with field survey data, is therefore suggested as a useful design improvement tool for installed reef structures and their deployment arrangement for recreational diving oases that can aid the sustainable development of the coastal zone.

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