水下集鱼灯在近海水体中的光场分布数值模拟

Numerical simulation on illumination distribution of underwater fishing lamp in offshore marine water

为提高水下集鱼灯光场分布计算精度,本实验采用集鱼灯光谱数据、光度分布数据和海水固有光学参数,基于蒙特卡罗模拟方法构建了新的光场传输数值模拟方法,将光束能量离散成大量光子,通过追踪光子路径计算水下集鱼灯形成的光场强度,并开展水槽实验对计算方法进行了验证。同时,提出了新的集鱼灯光场分布评价指标Ids和Ads。利用模型分析了海水的叶绿素a质量浓度、散射作用类型和散射相位函数HG(Henyey Greenstein)中非对称参量g的取值对水下光场分布的影响。结果显示,①叶绿素a质量浓度从1mg/m3增加到5 mg/m3,LED集鱼灯A5m减少了72.73%,MH集鱼灯A5m减少了72.17%;LED集鱼灯I5m减少了66.69%,MH集鱼灯I5m减少了53.29%。②当海水介质引起的散射类型分别为米氏散射和瑞利散射时,MH集鱼灯I5m分别为1058.48和1020.5 lx,LED集鱼灯I5m分别为1057.96和992.42 lx。③非对称参量g从0.80增加到0.99,MH集鱼灯的A5m增加了22.05%;LED集鱼灯的A5m增加了23.10%;MH集鱼灯形成的I5m增加了16.61%;LED集鱼灯形成的I5m增加了14.52%。研究表明,近海水体中叶绿素a质量浓度、HG散射函数中非对称参量对集鱼灯光场分布有显著影响,散射类型对集鱼灯光场分布无显著影响。本研究提出的数值模拟方法可准确计算近海水体中集鱼灯光场分布,为渔业监管和集鱼灯合理应用提供科学依据。

The illumination distribution in water is an important subject for efficient application research of fish-ing lamp.The traditional numerical calculation method could not accurately calculate the illumination distribution of the underwater fish gathering lamp in the offshore water.A new computing model of underwater illumination of fishing lamp was developed based on Monte Carlo method by using spectrum and luminous intensity of lamps and the inherent optical properties of seawater.Firstly,the vertical marine section was set as the target surface and divided it to some grids;secondly,photons with specific wavelength and direction were generated by random num-ber method,and then the attenuation coefficient of each photon was calculated by using chlorophyll concentration data,optical characteristics of pure seawater and its relationship with absorption and scattering coefficients;finally,all photons were emitted,and their transmission paths were tracked.The photons were recorded only if they fell into the target surface and the illuminance value of each grid was calculated according to the recorded position of A dsphotons.The calculation method was verified with flume test through collecting water samples.The—area of dsclosed region which enclosed by 0.1 lx contour line in marine section which m away from underwater fish-Idsing lamp and the—maximum illuminance value in marine section were used to characterize the spatial dis-tribution of light field in water.In this paper,the effect of chlorophyll concentrations,scattering type in the marine water and the scattering asymmetry parameters on the illumination distribution of LED fishing lamp and MH fishing lamp were analyzed through numerical simulation.The results showed:(1)with the chloro-A 5mphyll concentration increases from 1 mg/m3 to 5 mg/m3,the of LED lamp decreased from 1073.90 m2 to A 5m A 5m292.87 m2,which means has reduced by 72.73%;the of MH lamp decreased from 1094.51 m2 to 304.57 A 5m I5mm2,which means has reduced by 72.17%;the of MH decreased from 972.76 lx to 454.42 lx,which means I5m I5m I5mthe has reduced by 53.29%;the of LED decreased from 956.48 lx to 318.60 lx,which means the has I5mreduced by 66.69%.(2)when scattering type of the ocean water is Mie scattering and Rayleigh scattering,the of I5mMH is 956.48 lx and 318.60 lx,respectively;the of LED is 1057.96 lx and 992.42 lx,respectively.(3)with the A 5mscattering asymmetry parameters increases from 0.80 to 0.99,the of MH lamp decreased from 1094.89 m2 to 1336.40 A 5m A 5m A 5mm2,increased 22.05%;the of LED lamp decreased from 1076.52 m2 to 1325.21 m2,increased I5m I5m I5m23.10%;the of MH increased from 962.52 lx to 1122.48 lx,increased 16.62%;the of LED increased I5mfrom 980.74 lx to 1123.22 lx,increased 14.53%.It was found chlorophyll concentrations had a significant effect on illumination distribution of fishing lamp,while the scattering type and the scattering asymmetry paramet-ers on the illumination distribution had no significant effects.The numerical simulation method proposed in this paper can accurately calculate the illumination distribution of fishing lamps in offshore waters,which would provide scientific basis for fishery supervision and reasonable application of fishing lamps.