颗粒特性对矩形养殖舱中颗粒物去除效果的影响

Influence of particle characteristics on the removal of particles in the rectangular aquaculture tank

摘要:

养殖工船是拓展深远海养殖空间的新途径之一,在船载舱养过程中,如果未消化的饲料残渣和排泄物等颗粒物不能及时排出,则会对鱼类健康及其生长环境产生严重的负面影响。采用FLOW-3D软件进行数值仿真计算,研究了静止状态下30万t级养殖工船养殖舱出水口数目对舱内流场特征的影响,并在此基础上探究不同粒径与密度的颗粒物在舱内的去除效果。结果表明：当总进出水流量与出水口总面积恒定时,出水口数目从1增加到4,V_99%从0.244 m/s降低至0.232 m/s,V_95%从0.215 m/s降低至0.203 m/s,随着出水口数目的增加,养殖舱内流速减小；以占总量95%的颗粒物排出养殖舱所需时间为评价标准,当颗粒物密度为1 050 kg/m³时,粒径为1 mm的颗粒物排出需要约24 min,粒径为0.5 mm的颗粒物排出需要约45 min,粒径为0.1 mm的颗粒物排出需要约78 min,当颗粒物密度相同时,随着粒径增大,其在养殖舱内的停留时间减少；颗粒物粒径为1 mm时,密度为1 100 kg/m³的颗粒物排出需要约15 min,密度为1 150 kg/m³的颗粒物排出需要约11.6 min,当颗粒物粒径相同时,颗粒物密度越大,其在养殖舱流场内的停留时间越短。该研究形成了CFD数值仿真计算与数理统计有机结合的综合分析方法,为之后具有不同横摇周期和较大横摇幅值的复杂工况提供研究手段及理论依据。

Abstract:

Aquaculture vessels are one of the new ways to expand the space for offshore farming, and if particles such as undigested feed residues and excreta cannot be discharged in a timely manner during the shipboard tank farming process, it will have a serious negative impact on the health of fish and their growing environment. The article uses FLOW-3D software to carry out numerical simulation calculations to study the effect of the number of outlets in the aquaculture tank of the 300 000 t-class aquaculture vessel on the flow field characteristics under the stationary condition, and on this basis to explore the removal effect of particles with different particle sizes and densities in the tanks. The results showed that： when the total inlet and outlet flow rate and the total area of the outlet are constant, as the number of outlets increased from 1 to 4, V_99% decreased from 0.244 m/s to 0.232 m/s and V_95% decreased from 0.215 m/s to 0.203 m/s. As the number of outlets increases, the flow velocity in the aquaculture tank decreases. Measured by the time it takes for 95% of the total amount of particles to be discharged from the aquaculture tank, when the particle density was 1 050 kg/m³, discharge of particles with a particle size of 1 mm took about 24 minutes, discharge of particles with a particle size of 0.5 mm took about 45 minutes, and discharge of particles with a particle size of 0.1 mm took about 78 minutes. So at the same density of particles, as the particle size of particles increases, their retention time in the aquaculture tanks decreased and their removal efficiency increased significantly. When the particle size was 1 mm, discharge of particles with a density of 1 100 kg/m³ took about 15 minutes, and discharge of particles with a density of 1 150 kg/m³ took about 11.6 minutes. When the particle size of the particles was the same, the higher the density of the particles, the shorter their retention time in the flow field of the aquaculture tank, and the greater their removal efficiency. In this study, an integral analysis method combining CFD numerical simulation and mathematical statistics was formed to provide research means and theoretical basis for the complex working conditions with different transverse rolling periods and larger transverse rolling amplitudes.