以数值实验为基础的米字型鱼礁布设模式差异下的流场效率

人工鱼礁投放规模是鱼礁建设的核心问题之一,其中礁体数量与布设间距不仅表征了鱼礁规模的范围和密度,而且也决定着人工鱼礁流场效率。本研究采用数值实验方法,对典型结构边长为l的米字型人工鱼礁在4种投放量(2×2、3×3、4×4和5×5)、7种布设间距(0 l、0.5 l、1.0 l、1.5 l、2.0 l、3.0 l和4.0 l)下的流场相对体积、相对高度、相对长度等流场效率特性进行比较分析。结果显示,当上升流目标流速比分别为小于0.10、0.10～0.15和大于0.15倍时,上升流流场存在协同效应的最大布设间距分别为4.0 l、3.0 l、2.0 l,背涡流目标速度比下最大间距均为3.0 l;人工鱼礁投放量越多,上升流与背涡流相对体积越大,平均相对体积增长率越低,0.5 l布设间距的上升流相对体积与鱼礁单体相对流场体积最大,1.5 l布设间距的背涡流相对体积与鱼礁单体相对流场体积最大;上升流相对高度随投放量增加以1.01倍速率增加,随布设间距增加以0.90倍速率降低,背涡流相对长度随布设间距的增加先增后降,相对长度最大值位于1.0 l处。

Flow field efficiency of Mi-zi artificial reefs in different construction modes based on numerical experiments

The throwing scale of artificial reefs is one of the core issues in the construction of reefs. The throwing amount and disposal spacing of artificial reefs not only characterize the range and density, but also determine the efficiency of artificial reefs flow field effects. In our study, the flow field characteristics of seven disposal spacing (0 l, 0.5 l, 1.0 l, 1.5 l, 2.0 l, 3.0 l and 4.0 l) that is the multiple of the length of the single artificial reefs, with four throwing amounts of Mi-zi artificial reefs (2×2, 3×3, 4×4 and 5×5) were simulated using the large eddy simulation model based on the ANSYS software. Then, the relationships between the characteristics (including the relative volume, relative height and relative length) of different flow fields and the throwing amounts and disposal spacing and the target velocity ratio were studied. The results showed that when the upwelling target velocity ratio is less than 0.10, 0.10 to 0.15 and greater than 0.15 times, the maximum disposal spacing is 4.0 l, 3.0 l, 2.0 l, respectively, and there was a synergistic effect on the upwelling area. And the maximum disposal spacing is 3.0 l at all the back eddy target velocity ratios. The larger the reefing amount is, the higher the relative volume both the upwelling and the back eddy are, and the lower the average relative volume growth rate. At the disposal spacing of 0.5 l, the relative upwelling volume and the relative volume of the single artificial reefs are the largest, but the back eddy relative volume and the relative volume of the single artificial reefs are the largest at 1.5 l. The upwelling''s relative height increased at a rate of 1.01 times with the laying amount increasing and decreased at a rate of 0.90 times with the disposal spacing increasing, while the relative length of the back eddy would increase firstly and then decrease with the disposal spacing and the maximum at 1.0 l. The study provides the theoretical planning guidance for the artificial reef placement in different construction modes.