Wake Region Estimates of Artificial Reefs in Vietnam: Effects of Tropical Seawater Temperatures and Seasonal Water Flow Variation

Abstract

From the perspective of saving energy of marine species and creating feeding areas, the wake volume of an artificial reef (AR) should be considered as a parameter in any wake region estimation. Wake regions of AR modules (reef ball, cylinder reef, and cube reef) and sets were numerically estimated considering tropical seawater temperatures and water flow variation in Vietnamese coastal waters. In addition, we considered an efficiency index (i.e., total wake volume per reef volume) and wake volume diagram (i.e., wake volume dependency on water flow direction) to characterize wake volumes. From the results, first, it was found that the effect of temperature on the wake volumes was minor in comparison with the effect of flow direction. It was also found that the optimum installation angles were 30° (reef ball and its set), 30° (cylinder reef and its set), and 0° (cube and its set) along the major flow direction. Second, it was found that the cylinder reef and its set were attractive because they generated the maximum wake volumes, regardless of seawater temperature. Thus, the module and set showed better average efficiency indices (9.28 for module and 6.81 for set) than the other cases. We found that the wake volume was dominant in the efficiency index and, accordingly, wake volume diagrams are sufficient to indicate the dependence on flow direction.

An Experimental Investigation of Turbulence Features Induced by Typical Artificial M-Shaped Unit Reefs

“…Different configurations can in fact influence the flows passing through these structures, generating specific currents that could aid the deposition of solid material as well as the exchange of nutrients between multiple layers, with a consequent beneficial aspect for fish expansion [19,20]. Furthermore, these structures may also be used as protection or gathering areas by fish or other organisms, because the gentle and stable eddy currents created on the back of them could support the deposition of nutrients and function as a shield that is useful for avoiding enemies or larger predators [21][22][23][24][25][26][27].…”