isoAdvector是一种新的几何VOF(Volume of Fluid)方法,虽然克服了传统几何VOF方法难以适用于三维空间任意多面体网格的缺点,但不能直接用来模拟涉及动网格技术的液舱晃荡.为此,引入了运动通量修正,并提出了面-界面交线运动修正,使得修...isoAdvector是一种新的几何VOF(Volume of Fluid)方法,虽然克服了传统几何VOF方法难以适用于三维空间任意多面体网格的缺点,但不能直接用来模拟涉及动网格技术的液舱晃荡.为此,引入了运动通量修正,并提出了面-界面交线运动修正,使得修正后的isoAdvector方法可以应用到液舱晃荡的模拟中.基于不同的VOF方法对非共振、共振受迫晃荡和单次冲击波面进行数值模拟,并将模拟结果与试验结果以及解析解进行了比较.结果表明:相对于代数VOF方法,采用修正后的isoAdvector方法获得的自由液面位置和整体水动力载荷精度更高;捕捉的波面没有褶皱,能够较好地模拟波面的翻卷和破碎.此外,提出了界面厚度的估计方法,分析了自由液面波高精度提高的原因.展开更多
结合长距离无压引水隧洞充水过程,建立了水气两相流耦合VOF(Volume of Fluid)法的k-ε紊流模型,近壁面采用考虑糙率影响的壁面函数,结合实际工程对长距离无压引水隧洞水气两相流进行了模拟。模拟结果表明:隧洞内水位随充水时间的增加逐...结合长距离无压引水隧洞充水过程,建立了水气两相流耦合VOF(Volume of Fluid)法的k-ε紊流模型,近壁面采用考虑糙率影响的壁面函数,结合实际工程对长距离无压引水隧洞水气两相流进行了模拟。模拟结果表明:隧洞内水位随充水时间的增加逐渐上升并趋于稳定;对隧洞充水过程中沿程典型断面的水气两相流进行了动态分析,结果表明进口流量为65 m3/s时水流能顺利通过隧洞;对某水库放水兼放空洞水深实测数据进行了验证对比,模拟结果与实验结果基本吻合。展开更多
在CFD平台软件OpenFOAM上,用数值模拟的方法分析了变截面毛细流道中的毛细流动行为。该数值方法利用流体体积比函数(volume of fluid,VOF)来跟踪流体流动前沿界面,再用连续表面张力模型(continue surface force,CSF)来描述毛细驱动力。...在CFD平台软件OpenFOAM上,用数值模拟的方法分析了变截面毛细流道中的毛细流动行为。该数值方法利用流体体积比函数(volume of fluid,VOF)来跟踪流体流动前沿界面,再用连续表面张力模型(continue surface force,CSF)来描述毛细驱动力。VOF和CSF方法的结合使得毛细驱动力的求解能适应截面的变化。分别用该数值方法和解析方法对变间距平行平板间毛细流动进行了分析,发现两者的分析结果一致性较好。基于VOF和CSF的数值方法有望进一步应用于更复杂流场中的毛细流动分析。展开更多
针对浮式消波海流机样机测试时出现的问题,对其吃水深度线和叶片安装角度进行优化。根据装置结构特点,用Gambit建立了装置横截面的二维网格模型。根据浮式消波海流机实际工作环境,利用Fluent流体仿真软件,使用VOF(volume of fluid)两相...针对浮式消波海流机样机测试时出现的问题,对其吃水深度线和叶片安装角度进行优化。根据装置结构特点,用Gambit建立了装置横截面的二维网格模型。根据浮式消波海流机实际工作环境,利用Fluent流体仿真软件,使用VOF(volume of fluid)两相流模型,分配空气相与液态水相在流域中的不同比例,来确定不同的吃水深度线。并且结合k-epsilon紊流模型建立模拟仿真环境。先对3种水线进行仿真分析,然后进行实验验证。通过分析对比装置的3种不同吃水深度线的模拟与实验结果,得到装置的最优吃水深度线为1/3水线。基于最优吃水深度线,分别对叶片的4种安装角度在相同的仿真环境中进行模拟仿真。利用仿真得到的扭矩数据,计算扭矩系数、功率系数,分析对比仿真数据以及仿真过程中扭矩趋势图得出4种叶片安装角度的最优角度是90°。吃水深度线决定了装置的消波能力,并且为叶片获能提供条件,叶片安装角度直接影响着装置的获能效率,所以最优的吃水深度线和叶片安装角度对海流机的消波能力和获能效率具有重要意义。展开更多
基于大涡模拟(large eddy simulation,LES)和流体体积(volume of fluid,VOF)法对同轴双通道气-液射流进行了3D数值模拟,用LES法求解气液相的流场,VOF法捕捉运动的气液界面.数值模拟结果表明,随着韦伯数(We)的增大,液体破裂出现了轴对称...基于大涡模拟(large eddy simulation,LES)和流体体积(volume of fluid,VOF)法对同轴双通道气-液射流进行了3D数值模拟,用LES法求解气液相的流场,VOF法捕捉运动的气液界面.数值模拟结果表明,随着韦伯数(We)的增大,液体破裂出现了轴对称模式和非轴对称模式,以破裂长度、未扰动长度及破裂形态为表征液体射流的特征量与实验值进行了对比,得到了较好的一致性.展开更多
Taking the ratio of heat transfer area to net power and heat recovery efficiency into account, a multi-objective mathematical model was developed for organic Rankine cycle （ORC）. Working fluids considered were R123,...Taking the ratio of heat transfer area to net power and heat recovery efficiency into account, a multi-objective mathematical model was developed for organic Rankine cycle （ORC）. Working fluids considered were R123, R134a, R141b, R227ea and R245fa. Under the given conditions, the parameters including evaporating and condensing pressures, working fluid and cooling water velocities were optimized by simulated annealing algorithm. The results show that the optimal evaporating pressure increases with the heat source temperature increasing. Compared with other working fluids, R123 is the best choice for the temperature range of 100--180℃ and R141 b shows better performance when the temperature is higher than 180 ℃. Economic characteristic of system decreases rapidly with the decrease of heat source temperature. ORC system is uneconomical for the heat source temperature lower than 100℃.展开更多
Aiming at the demand for optimization of hydrodynamic coefficients in submarine's motion equations,an adaptive weight immune genetic algorithm was proposed to optimize hydrodynamic coefficients in motion equations...Aiming at the demand for optimization of hydrodynamic coefficients in submarine's motion equations,an adaptive weight immune genetic algorithm was proposed to optimize hydrodynamic coefficients in motion equations.Some hydrodynamic coefficients of high sensitivity to control and maneuver were chosen as the optimization objects in the algorithm.By using adaptive weight method to determine the weight and target function,the multi-objective optimization could be translated into single-objective optimization.For a certain kind of submarine,three typical maneuvers were chosen to be the objects of study:overshoot maneuver in horizontal plane,overshoot maneuver in vertical plane and turning circle maneuver in horizontal plane.From the results of computer simulations using primal hydrodynamic coefficient and optimized hydrodynamic coefficient,the efficiency of proposed method is proved.展开更多
文摘isoAdvector是一种新的几何VOF(Volume of Fluid)方法,虽然克服了传统几何VOF方法难以适用于三维空间任意多面体网格的缺点,但不能直接用来模拟涉及动网格技术的液舱晃荡.为此,引入了运动通量修正,并提出了面-界面交线运动修正,使得修正后的isoAdvector方法可以应用到液舱晃荡的模拟中.基于不同的VOF方法对非共振、共振受迫晃荡和单次冲击波面进行数值模拟,并将模拟结果与试验结果以及解析解进行了比较.结果表明:相对于代数VOF方法,采用修正后的isoAdvector方法获得的自由液面位置和整体水动力载荷精度更高;捕捉的波面没有褶皱,能够较好地模拟波面的翻卷和破碎.此外,提出了界面厚度的估计方法,分析了自由液面波高精度提高的原因.
文摘结合长距离无压引水隧洞充水过程,建立了水气两相流耦合VOF(Volume of Fluid)法的k-ε紊流模型,近壁面采用考虑糙率影响的壁面函数,结合实际工程对长距离无压引水隧洞水气两相流进行了模拟。模拟结果表明:隧洞内水位随充水时间的增加逐渐上升并趋于稳定;对隧洞充水过程中沿程典型断面的水气两相流进行了动态分析,结果表明进口流量为65 m3/s时水流能顺利通过隧洞;对某水库放水兼放空洞水深实测数据进行了验证对比,模拟结果与实验结果基本吻合。
文摘在CFD平台软件OpenFOAM上,用数值模拟的方法分析了变截面毛细流道中的毛细流动行为。该数值方法利用流体体积比函数(volume of fluid,VOF)来跟踪流体流动前沿界面,再用连续表面张力模型(continue surface force,CSF)来描述毛细驱动力。VOF和CSF方法的结合使得毛细驱动力的求解能适应截面的变化。分别用该数值方法和解析方法对变间距平行平板间毛细流动进行了分析,发现两者的分析结果一致性较好。基于VOF和CSF的数值方法有望进一步应用于更复杂流场中的毛细流动分析。
文摘针对浮式消波海流机样机测试时出现的问题,对其吃水深度线和叶片安装角度进行优化。根据装置结构特点,用Gambit建立了装置横截面的二维网格模型。根据浮式消波海流机实际工作环境,利用Fluent流体仿真软件,使用VOF(volume of fluid)两相流模型,分配空气相与液态水相在流域中的不同比例,来确定不同的吃水深度线。并且结合k-epsilon紊流模型建立模拟仿真环境。先对3种水线进行仿真分析,然后进行实验验证。通过分析对比装置的3种不同吃水深度线的模拟与实验结果,得到装置的最优吃水深度线为1/3水线。基于最优吃水深度线,分别对叶片的4种安装角度在相同的仿真环境中进行模拟仿真。利用仿真得到的扭矩数据,计算扭矩系数、功率系数,分析对比仿真数据以及仿真过程中扭矩趋势图得出4种叶片安装角度的最优角度是90°。吃水深度线决定了装置的消波能力,并且为叶片获能提供条件,叶片安装角度直接影响着装置的获能效率,所以最优的吃水深度线和叶片安装角度对海流机的消波能力和获能效率具有重要意义。
文摘基于大涡模拟(large eddy simulation,LES)和流体体积(volume of fluid,VOF)法对同轴双通道气-液射流进行了3D数值模拟,用LES法求解气液相的流场,VOF法捕捉运动的气液界面.数值模拟结果表明,随着韦伯数(We)的增大,液体破裂出现了轴对称模式和非轴对称模式,以破裂长度、未扰动长度及破裂形态为表征液体射流的特征量与实验值进行了对比,得到了较好的一致性.
基金Project(2009GK2009) supported by Science and Technology Department Funds of Hunan Province,ChinaProject(08C26224302178) supported by Innovation Fund for Technology Based Firms of China
文摘Taking the ratio of heat transfer area to net power and heat recovery efficiency into account, a multi-objective mathematical model was developed for organic Rankine cycle （ORC）. Working fluids considered were R123, R134a, R141b, R227ea and R245fa. Under the given conditions, the parameters including evaporating and condensing pressures, working fluid and cooling water velocities were optimized by simulated annealing algorithm. The results show that the optimal evaporating pressure increases with the heat source temperature increasing. Compared with other working fluids, R123 is the best choice for the temperature range of 100--180℃ and R141 b shows better performance when the temperature is higher than 180 ℃. Economic characteristic of system decreases rapidly with the decrease of heat source temperature. ORC system is uneconomical for the heat source temperature lower than 100℃.
文摘Aiming at the demand for optimization of hydrodynamic coefficients in submarine's motion equations,an adaptive weight immune genetic algorithm was proposed to optimize hydrodynamic coefficients in motion equations.Some hydrodynamic coefficients of high sensitivity to control and maneuver were chosen as the optimization objects in the algorithm.By using adaptive weight method to determine the weight and target function,the multi-objective optimization could be translated into single-objective optimization.For a certain kind of submarine,three typical maneuvers were chosen to be the objects of study:overshoot maneuver in horizontal plane,overshoot maneuver in vertical plane and turning circle maneuver in horizontal plane.From the results of computer simulations using primal hydrodynamic coefficient and optimized hydrodynamic coefficient,the efficiency of proposed method is proved.
