Wave-induced sound pressure from artificial fish reefs and applicability to sea environment improvement

对1996年实验中使用的二维结构绕流进行了精确的数值计算。计算了压力振动，分析了压力振动的时间变化和幅值谱。在结构周围形成的旋涡及其行为与实验中观察到的旋涡非常相似。虽然在模拟中不能很好地再现压力下的高频振动，但可以很好地模拟出振幅谱在一定的频域内有所增加。这与实验结果在定性上是一致的。还利用立方型鱼礁模型在三维波浪水池中进行了实验室实验。在实验中，研究了鱼礁数目及其排列方式对声压的影响。在实验研究的基础上，得到了以下结论：1)在原有鱼礁的基础上再加一个鱼礁，增大了鱼礁之间的声速，但不增加声压。在鱼礁阵列的外部区域也得到了类似的结果。2)安装另一个鱼礁阵列可以增大鱼礁外角前面的声压。这些结果表明，波浪与一组鱼礁、水流与每个鱼礁之间的相互作用的综合作用对局部声压特性有重要影响。由此可见，在安装鱼礁时，必须对有关安排进行详细调查。

Precise numerical calculation is performed to simulate a flow around two-dimensional structures which were emploved in the experiments carried out in 1996. The pressure vibration are also calculated and their time variations and amplitude spectra are analyzed. The vortices formed around the structure and their behaviors are confirmed to be very similar to those observed in the experiments. Although, the high frequency vibration in the pressure was not able to be reproduced well in the simulation, the amplitude spectrum was well simulated to be increased in a certain frequency domain. This agree with the experimental results in qualitative.Laboratory experiments are also conducted in the three dimensional wave basin using cubic type fish reef models. In the experiments effects of number of fish reef and their arrangements on the sound pressure are investigated. Based on the experimental study, following results are obtaind.1) The installing another fish reef beside the existing one enlarges the velocity between the reefs, however, it does not increase the sound pressure. Similar result is obtained in outer region of the array of the fish reefs.2) The sound pressure in front of the outer corner of the fish reef is enlarged by installing another one. These results suggest that the combined effect of interactions between wave and a group of fish reefs and between flow and each fish reef plays important roles on the characteristics of local sound pressure. This indicates the detail investigations on the arrangement are necessary in installing the fish reefs.