根据Level-Set方法和VOF方法的优缺点,近年来兴起了一类界面追踪的耦合方法——CLSVOF(Coupled Level-Set and Volume-of-Fluid Method)方法。本文阐述了该方法的耦合实现过程,通过旋转流场和剪切流场2个算例验证了CLSVOF方法相比Level-...根据Level-Set方法和VOF方法的优缺点,近年来兴起了一类界面追踪的耦合方法——CLSVOF(Coupled Level-Set and Volume-of-Fluid Method)方法。本文阐述了该方法的耦合实现过程,通过旋转流场和剪切流场2个算例验证了CLSVOF方法相比Level-Set方法实现了计算过程中的物理量守恒,克服了VOF方法难以准确计算界面的法向和曲率的缺点。使用该方法对溃坝模型进行计算,并将数值模拟结果进行对比分析。结果表明:CLSVOF方法计算结果更加接近于实验结果,该方法相比其他界面追踪方法具有更高的运动界面追踪分辨率。由此说明CLSVOF方法模拟具有自由表面流动工程实际问题的精确性和可行性。展开更多
The sediment suspension and transport process under complex breaking wave situation is investigated using large eddy simulation (abbreviated as LES hereafter) method. The coupled level set (LS) and volume of fluid (VO...The sediment suspension and transport process under complex breaking wave situation is investigated using large eddy simulation (abbreviated as LES hereafter) method. The coupled level set (LS) and volume of fluid (VOF) method is used to accurately capture the evolution of air-water interface. The wall effect at the bottom is modeled based on the wave friction term while the complicate bottom boundary condition for sediment is tackled using Chou and Fringer's sediment erosion and deposition flux method. A simulation is carried out to study the sediment suspension and transport process under periodic plunging breaking waves. The comparison between the results by CLSVOF method and those obtained by the LS method is given. It shows that the latter performs as well as the CLSVOF method in the pre-breaking weak-surface deformation situation. However, a serious mass conservation problem in the later stages of wave breaking makes it inappropriate for this study by use of the LS method and thus the CLSVOF method is suggested. The flow field and the distribution of suspended sediment concentration are then analyzed in detail. At the early stage of breaking, the sediment is mainly concentrated near the bottom area. During the wave breaking process, when the entrapped large-scale air bubble travels downward to approach the bottom, strong shear is induced and the sediment is highly entrained.展开更多
采用CLSVOF（coupled level set and volume of fluid method）方法,以空气和水为介质对矩形截面螺旋管内气液两相流动进行数值模拟,气相折算速度UG为0.1～2.5 m·s^-1,液相折算速度UL为0.09～4.5 m·s^-1。研究螺旋直径、螺旋...采用CLSVOF（coupled level set and volume of fluid method）方法,以空气和水为介质对矩形截面螺旋管内气液两相流动进行数值模拟,气相折算速度UG为0.1～2.5 m·s^-1,液相折算速度UL为0.09～4.5 m·s^-1。研究螺旋直径、螺旋升角对流型转换边界的影响,并绘制了不同螺旋直径、不同螺旋升角下的流型图。数值结果表明,与传统VOF方法相比,CLSVOF可以得到更精确的相界面;随着螺旋升角的增加,塞状流向泡状流的转换边界向UL减小的方向进行,但是幅度很小,塞状流向弹状流的转换边界向UL减小的方向进行;随着螺旋直径的增加,塞状流向泡状流的转换边界向UL减小的方向进行,塞状流向弹状流的转换边界向UL减小、UG增大的方向进行;与Murai流型图相比,流型转换边界有所差异。展开更多
文摘根据Level-Set方法和VOF方法的优缺点,近年来兴起了一类界面追踪的耦合方法——CLSVOF(Coupled Level-Set and Volume-of-Fluid Method)方法。本文阐述了该方法的耦合实现过程,通过旋转流场和剪切流场2个算例验证了CLSVOF方法相比Level-Set方法实现了计算过程中的物理量守恒,克服了VOF方法难以准确计算界面的法向和曲率的缺点。使用该方法对溃坝模型进行计算,并将数值模拟结果进行对比分析。结果表明:CLSVOF方法计算结果更加接近于实验结果,该方法相比其他界面追踪方法具有更高的运动界面追踪分辨率。由此说明CLSVOF方法模拟具有自由表面流动工程实际问题的精确性和可行性。
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51409195 and 51379155)the Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2013491111)+2 种基金the China Postdoctoral Science Foundation(Grant No.2014M550408)the Fundamental Research Funds for the Central Universities(Grant No.2042014kf0068)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(China Institute of Water Resources and Hydropower Research,Grant No.IWHR-SKL-201112)
文摘The sediment suspension and transport process under complex breaking wave situation is investigated using large eddy simulation (abbreviated as LES hereafter) method. The coupled level set (LS) and volume of fluid (VOF) method is used to accurately capture the evolution of air-water interface. The wall effect at the bottom is modeled based on the wave friction term while the complicate bottom boundary condition for sediment is tackled using Chou and Fringer's sediment erosion and deposition flux method. A simulation is carried out to study the sediment suspension and transport process under periodic plunging breaking waves. The comparison between the results by CLSVOF method and those obtained by the LS method is given. It shows that the latter performs as well as the CLSVOF method in the pre-breaking weak-surface deformation situation. However, a serious mass conservation problem in the later stages of wave breaking makes it inappropriate for this study by use of the LS method and thus the CLSVOF method is suggested. The flow field and the distribution of suspended sediment concentration are then analyzed in detail. At the early stage of breaking, the sediment is mainly concentrated near the bottom area. During the wave breaking process, when the entrapped large-scale air bubble travels downward to approach the bottom, strong shear is induced and the sediment is highly entrained.
文摘采用CLSVOF（coupled level set and volume of fluid method）方法,以空气和水为介质对矩形截面螺旋管内气液两相流动进行数值模拟,气相折算速度UG为0.1～2.5 m·s^-1,液相折算速度UL为0.09～4.5 m·s^-1。研究螺旋直径、螺旋升角对流型转换边界的影响,并绘制了不同螺旋直径、不同螺旋升角下的流型图。数值结果表明,与传统VOF方法相比,CLSVOF可以得到更精确的相界面;随着螺旋升角的增加,塞状流向泡状流的转换边界向UL减小的方向进行,但是幅度很小,塞状流向弹状流的转换边界向UL减小的方向进行;随着螺旋直径的增加,塞状流向泡状流的转换边界向UL减小的方向进行,塞状流向弹状流的转换边界向UL减小、UG增大的方向进行;与Murai流型图相比,流型转换边界有所差异。
