A Fundamental Study on the Steel Artificial Reefs at a Fishing Ground with Hydrodynamic Evaluation Model

Abstract

The artificial reefs are developed for the fish accumulation. Many physical characteristics were studied for improving the stability of artificial reefs against flows. This study aims to identify flow patterns, especially the wakes around the two-layer steel cubic artificial reef, which has more stability to the inflow compared to others, under the various flow and artificial reef conditions. FLOW3D hydrodynamic model which is based on the VOF method is used for simulating flow patterns behind the artificial reef. Model inputs and a artificial reef for the FLOW3D computations are designed based on the existing literatures which was focused on the artificial reef in the field site, e.g. Gijang. The main results from the study is summarized as below. (1) The simulated flows present quite different patterns depending on the porosity of a artificial reef. However, the influences of the inflow condition such as the maximum current velocity are insignificant. Especially, in the case of impermeable artificial reef which has no porosity the strong clockwise circulation like wakes are occurred behind of it, but with a artificial reef porosity of 0.983 the pattern only was shown in the flow pattern. (2) The length of wake ranges are generally increased, as the porosity of the artificial reef is reduced or the inflow velocity is increased. (3) This study investigated the wake lengths are increased with the increase of Reynolds Number, that is introduced in the previous research based on the hydraulic experiments using different type of artificial reefs. This confirms the availability of the numerical application for the wake study. More studies considered detailed conditions for the artificial reef is required for the future study.