基于两相界面追踪流体体积(volume of fluid,简称VOF)方法模拟了离心式喷嘴内部的流动过程,在数值方法可靠性验证基础上,得到了15个喷嘴构型的流量系数、液膜厚度以及雾化锥角.定义无量纲影响因子η,比较喷嘴结构参数对喷嘴性能的影响程...基于两相界面追踪流体体积(volume of fluid,简称VOF)方法模拟了离心式喷嘴内部的流动过程,在数值方法可靠性验证基础上,得到了15个喷嘴构型的流量系数、液膜厚度以及雾化锥角.定义无量纲影响因子η,比较喷嘴结构参数对喷嘴性能的影响程度.除了喷嘴直径和旋流室直径外,重点研究了出口扩张角、等直段长径比等结构参数的影响,通过与试验相对比,综合以往经验公式,得到如下结论:增大旋流室长度,能够增大雾化锥角;在喷嘴出口增加扩张角,能够显著地减小液膜厚度,减小雾化锥角;增大切向口距喷嘴顶部距离,能够改善喷嘴性能;切向口个数和等直段长度对喷嘴性能影响不大.该工作为下一步优化喷嘴构型打下了基础.展开更多
Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） method.Extreme waves are generated based on wave focusing in a 2-D numerical model.To validate the capability of the...Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） method.Extreme waves are generated based on wave focusing in a 2-D numerical model.To validate the capability of the VOF-based model described in this article,the propagation of regular waves is computed and compared with the theoretical results.By adjusting the phases of wave components,extreme waves are formed at given time and given position in the computation.The numerical results are compared with theoretical solutions and experimental data.It is concluded that the present model based on the VOF technique can provide acceptably accurate numerical results to serve practical purposes.展开更多
基于两相界面追踪方法 VOF(volume of fluid)模拟了离心式喷嘴内部的流动过程,得到了液相填充喷嘴内部的过程,初始时刻,气液界面出现褶皱,随着进入液体的增多,褶皱逐渐消失;着重分析了喷嘴各个部位速度、压力分布,由于气液两相的存在,...基于两相界面追踪方法 VOF(volume of fluid)模拟了离心式喷嘴内部的流动过程,得到了液相填充喷嘴内部的过程,初始时刻,气液界面出现褶皱,随着进入液体的增多,褶皱逐渐消失;着重分析了喷嘴各个部位速度、压力分布,由于气液两相的存在,喷嘴内部流场变得异常复杂,流场分布不能用单相流的模式分析,总压损失大部分存在于喷嘴收缩段以及直管段,增大收缩段锥角、减小收缩段长度有利于减小总压损失;在喷嘴出口处设置一定扩张角,能够增加液相速度,减小液膜厚度,有利于雾化.展开更多
为了提高航空发动机离心喷嘴的雾化性能,优化喷嘴喷口结构参数,基于两相界面追踪流体体积(Volume of fluid,VOF)方法对离心喷嘴进行了仿真分析,并通过实验验证了VOF方法的可靠性。采用正交试验方法完成以喷嘴出口直径、出口直管段长度...为了提高航空发动机离心喷嘴的雾化性能,优化喷嘴喷口结构参数,基于两相界面追踪流体体积(Volume of fluid,VOF)方法对离心喷嘴进行了仿真分析,并通过实验验证了VOF方法的可靠性。采用正交试验方法完成以喷嘴出口直径、出口直管段长度、扩张角、扩张段长度为优化参数,以雾化锥角、液膜厚度和流量系数作为雾化性能指标的试验设计。通过极差方差分析讨论各个参数对雾化性能指标影响的显著性并利用回归分析得到规律曲线,获得最佳参数组合。结果表明:4个结构参数中扩张角是对喷嘴雾化性能影响最大的因素;扩张角和喷口直径的增大可以明显地增大雾化锥角,减小液膜厚度和流量系数;扩张段长度的增大会使雾化锥角减小,同时减小液膜厚度和流量系数;直管段长度的变化对各指标的影响不大;当扩张角θ为60°,出口直径D为0.6mm,出口直管段长度L1为0.3mm,扩张段长度L2为0.4mm时,雾化性能最佳。展开更多
The Chinese sturgeon （Acipenser Sinensis） is one of the unique and important fishery resources in China. Since the construction of the Gezhouba Dam, the traditional migration route of the sturgeon has been blocked; ...The Chinese sturgeon （Acipenser Sinensis） is one of the unique and important fishery resources in China. Since the construction of the Gezhouba Dam, the traditional migration route of the sturgeon has been blocked; consequently, the length of natural spawning sites is reduced from 800 km in the past to less than 5 km at present. As an endangered species, the Chinese sturgeon has become one of the most conserved aquatic species. In this article, the flow field of its spawning states in the downstream of Gezhouba Dam was simulated and analyzed using N-S equations and k-ε turbulence model. Volume Of Fluid （VOF） method with the Finite Volume Method （FVM） was used to simulate the water-air two-phase flow to examine the computed area. On the basis of the ecological-hydraulic characteristics of Chinese sturgeon, the features of the flow field were investigated to provide theoretical support for the proper management of the Three Gorges Reservoir.展开更多
基于两相界面追踪方法 VOF(volume of fluid)模拟了离心式喷嘴充填过程中的内部流动特性。研究了气液界面随时间的变化过程,发现了充填过程中气核收缩和旋转液膜的现象;通过提取气相体积分数等值线的方法计算了充填过程中喷嘴出口液膜...基于两相界面追踪方法 VOF(volume of fluid)模拟了离心式喷嘴充填过程中的内部流动特性。研究了气液界面随时间的变化过程,发现了充填过程中气核收缩和旋转液膜的现象;通过提取气相体积分数等值线的方法计算了充填过程中喷嘴出口液膜厚度和喷雾锥角的变化。结果发现:液膜厚度随出口流量的增大而增大,出口喷雾锥角随出口流量的增大而减小;描述了喷嘴旋流室内的回流现象,分析了充填完成后的压力场和速度场分布,发现在压降和气液作用的共同影响下,中心气核轴向速度沿轴向先增后减。展开更多
A new method for sloshing simulation in a sway tank is present, in which the two phase interface is treated as a physical discontinuity, which can be captured by a well-designed high order scheme. Based on Normalized ...A new method for sloshing simulation in a sway tank is present, in which the two phase interface is treated as a physical discontinuity, which can be captured by a well-designed high order scheme. Based on Normalized Variable Diagram （NVD）, a high order discretization scheme with unstructured grids is realized, together with a numerical method for free surface flow with a fixed grid. This method is implemented in an in-house code General Transport Equation Analyzer （ GTEA ） which is an unstructured grids finite volume solver. The present method is first validated by available analytical solutions. A simulation for a 2-D rectangular tank at different excitation frequencies of the sway is carried out. A comparison with experimental data in literature and results obtained by commercial software CFX shows that the sloshing load on the monitor points agrees well with the experimental data, with the same grids, and the present method gives better results on the secondary peak. It is shown that the present method can simulate the free surface overturning and breakup phenomena.展开更多
In real sea states,damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave...In real sea states,damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave train.So,using CFD tools to precisely simulate predetermined irregular wave train will lay sound basis for understanding the local characteristic of the flow field and impact loads on offshore floating structures when damage incidents occur.In this article,the generation of single extreme wave is investigated in a numerical wave tank.First,experimental irregular wave train is decomposed into certain number of small-amplitude waves.The Fourier series expansion is performed to determine the amplitude and initial phase angle of each wave component.A hydrodynamic transfer function is used to calculate the amplitude of wave-maker motion associated with each wave component.Then superposition is carried out on all of the wave-maker motion components to get the final wave-maker motion.With the wave-maker motion as input,simulation of the single extreme irregular wave train is modeled successfully.Then the method is applied to simulating a much more complicated irregular wave train.Once again main features of the complicated irregular wave train are reproduced compared with experiment carried out in the new deepwater experimental basin at Shanghai Jiao Tong University.In the simulation,dynamic mesh method is enabled to model the piston-type wave-maker,the Volume Of Fluid（VOF） method is employed to capture the free surface and a dissipation zone is introduced to deal with wave reflection.展开更多
文摘基于两相界面追踪流体体积(volume of fluid,简称VOF)方法模拟了离心式喷嘴内部的流动过程,在数值方法可靠性验证基础上,得到了15个喷嘴构型的流量系数、液膜厚度以及雾化锥角.定义无量纲影响因子η,比较喷嘴结构参数对喷嘴性能的影响程度.除了喷嘴直径和旋流室直径外,重点研究了出口扩张角、等直段长径比等结构参数的影响,通过与试验相对比,综合以往经验公式,得到如下结论:增大旋流室长度,能够增大雾化锥角;在喷嘴出口增加扩张角,能够显著地减小液膜厚度,减小雾化锥角;增大切向口距喷嘴顶部距离,能够改善喷嘴性能;切向口个数和等直段长度对喷嘴性能影响不大.该工作为下一步优化喷嘴构型打下了基础.
基金support by the National Natural Science Foundation of China (Grant No. 50779004)
文摘Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） method.Extreme waves are generated based on wave focusing in a 2-D numerical model.To validate the capability of the VOF-based model described in this article,the propagation of regular waves is computed and compared with the theoretical results.By adjusting the phases of wave components,extreme waves are formed at given time and given position in the computation.The numerical results are compared with theoretical solutions and experimental data.It is concluded that the present model based on the VOF technique can provide acceptably accurate numerical results to serve practical purposes.
文摘基于两相界面追踪方法 VOF(volume of fluid)模拟了离心式喷嘴内部的流动过程,得到了液相填充喷嘴内部的过程,初始时刻,气液界面出现褶皱,随着进入液体的增多,褶皱逐渐消失;着重分析了喷嘴各个部位速度、压力分布,由于气液两相的存在,喷嘴内部流场变得异常复杂,流场分布不能用单相流的模式分析,总压损失大部分存在于喷嘴收缩段以及直管段,增大收缩段锥角、减小收缩段长度有利于减小总压损失;在喷嘴出口处设置一定扩张角,能够增加液相速度,减小液膜厚度,有利于雾化.
文摘为了提高航空发动机离心喷嘴的雾化性能,优化喷嘴喷口结构参数,基于两相界面追踪流体体积(Volume of fluid,VOF)方法对离心喷嘴进行了仿真分析,并通过实验验证了VOF方法的可靠性。采用正交试验方法完成以喷嘴出口直径、出口直管段长度、扩张角、扩张段长度为优化参数,以雾化锥角、液膜厚度和流量系数作为雾化性能指标的试验设计。通过极差方差分析讨论各个参数对雾化性能指标影响的显著性并利用回归分析得到规律曲线,获得最佳参数组合。结果表明:4个结构参数中扩张角是对喷嘴雾化性能影响最大的因素;扩张角和喷口直径的增大可以明显地增大雾化锥角,减小液膜厚度和流量系数;扩张段长度的增大会使雾化锥角减小,同时减小液膜厚度和流量系数;直管段长度的变化对各指标的影响不大;当扩张角θ为60°,出口直径D为0.6mm,出口直管段长度L1为0.3mm,扩张段长度L2为0.4mm时,雾化性能最佳。
基金Project supported by the Three Georges Construction Commission and the National Natural Science Foundation of China (Grant No. 30490231).
文摘The Chinese sturgeon （Acipenser Sinensis） is one of the unique and important fishery resources in China. Since the construction of the Gezhouba Dam, the traditional migration route of the sturgeon has been blocked; consequently, the length of natural spawning sites is reduced from 800 km in the past to less than 5 km at present. As an endangered species, the Chinese sturgeon has become one of the most conserved aquatic species. In this article, the flow field of its spawning states in the downstream of Gezhouba Dam was simulated and analyzed using N-S equations and k-ε turbulence model. Volume Of Fluid （VOF） method with the Finite Volume Method （FVM） was used to simulate the water-air two-phase flow to examine the computed area. On the basis of the ecological-hydraulic characteristics of Chinese sturgeon, the features of the flow field were investigated to provide theoretical support for the proper management of the Three Gorges Reservoir.
文摘基于两相界面追踪方法 VOF(volume of fluid)模拟了离心式喷嘴充填过程中的内部流动特性。研究了气液界面随时间的变化过程,发现了充填过程中气核收缩和旋转液膜的现象;通过提取气相体积分数等值线的方法计算了充填过程中喷嘴出口液膜厚度和喷雾锥角的变化。结果发现:液膜厚度随出口流量的增大而增大,出口喷雾锥角随出口流量的增大而减小;描述了喷嘴旋流室内的回流现象,分析了充填完成后的压力场和速度场分布,发现在压降和气液作用的共同影响下,中心气核轴向速度沿轴向先增后减。
基金Project supported by the China Postdoctoral Science Foundation (Grant No. 20100471016)the Fundamental Research Funds for Major Universities (Grant No. HEUCF 100307)
文摘A new method for sloshing simulation in a sway tank is present, in which the two phase interface is treated as a physical discontinuity, which can be captured by a well-designed high order scheme. Based on Normalized Variable Diagram （NVD）, a high order discretization scheme with unstructured grids is realized, together with a numerical method for free surface flow with a fixed grid. This method is implemented in an in-house code General Transport Equation Analyzer （ GTEA ） which is an unstructured grids finite volume solver. The present method is first validated by available analytical solutions. A simulation for a 2-D rectangular tank at different excitation frequencies of the sway is carried out. A comparison with experimental data in literature and results obtained by commercial software CFX shows that the sloshing load on the monitor points agrees well with the experimental data, with the same grids, and the present method gives better results on the secondary peak. It is shown that the present method can simulate the free surface overturning and breakup phenomena.
基金supported by the National High Technology Research and Development Program of China (863 Program,Grant No. 2006AA09A107)the National Natural Science Foundation of China (Grant No. 50709079)
文摘In real sea states,damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave train.So,using CFD tools to precisely simulate predetermined irregular wave train will lay sound basis for understanding the local characteristic of the flow field and impact loads on offshore floating structures when damage incidents occur.In this article,the generation of single extreme wave is investigated in a numerical wave tank.First,experimental irregular wave train is decomposed into certain number of small-amplitude waves.The Fourier series expansion is performed to determine the amplitude and initial phase angle of each wave component.A hydrodynamic transfer function is used to calculate the amplitude of wave-maker motion associated with each wave component.Then superposition is carried out on all of the wave-maker motion components to get the final wave-maker motion.With the wave-maker motion as input,simulation of the single extreme irregular wave train is modeled successfully.Then the method is applied to simulating a much more complicated irregular wave train.Once again main features of the complicated irregular wave train are reproduced compared with experiment carried out in the new deepwater experimental basin at Shanghai Jiao Tong University.In the simulation,dynamic mesh method is enabled to model the piston-type wave-maker,the Volume Of Fluid（VOF） method is employed to capture the free surface and a dissipation zone is introduced to deal with wave reflection.
