采用数值模拟的方法,对在重力作用下微管末端液滴缓慢形成及脱落的动力学过程进行分析和研究。采用有限体积法在轴对称坐标系下求解液滴形成与破碎过程的Navier-Stokes方程,采用VOF(volume of fluid)方法以及基于PLIC(piecewise-linear ...采用数值模拟的方法,对在重力作用下微管末端液滴缓慢形成及脱落的动力学过程进行分析和研究。采用有限体积法在轴对称坐标系下求解液滴形成与破碎过程的Navier-Stokes方程,采用VOF(volume of fluid)方法以及基于PLIC(piecewise-linear interface construction)的几何重构方法追踪液滴运动过程的自由表面,捕捉气液界面的演化过程。分析了量纲1液滴最小颈宽以及量纲1液滴高度等相关特征量随相对时间的变化规律,并与实验结果进行了比较。分析了液滴形貌与液滴轴心线上流向速度的变化以及液滴内部涡环形成与湮灭的关系。通过研究轴心线上压力随时间的变化,分析了压力与液滴颈部位置及断裂位置的关系。展开更多
基于海洋石油平台系统特征,比较分析了火炬系统的两种热辐射模型,建立了适用于水幕系统的两通量隔热模型.通过实验数据对比,验证了模型的适用性.结果表明,Thornton辐射模型比API RP 521标准中的方法更为合理;雾场特性参数对水幕系统的...基于海洋石油平台系统特征,比较分析了火炬系统的两种热辐射模型,建立了适用于水幕系统的两通量隔热模型.通过实验数据对比,验证了模型的适用性.结果表明,Thornton辐射模型比API RP 521标准中的方法更为合理;雾场特性参数对水幕系统的隔热效果有着很大的影响,水幕透射率随着液滴出口压力的增大而逐渐减小,但影响幅度逐渐减少.基于该模型所得到的实际海洋石油平台的火炬辐射水幕隔热系统的设计证明了该模型具有较好的合理性及较强的工程适用性.展开更多
The streamwise velocity components at different vertical heights in wall turbulence were measured. Wavelet transform was used to study the turbulent energy spectra, indicating that the global spectrum results from the...The streamwise velocity components at different vertical heights in wall turbulence were measured. Wavelet transform was used to study the turbulent energy spectra, indicating that the global spectrum results from the weighted average of Fourier spectrum based on wavelet scales. W＇avelet transform with more vanishing moments can express the declining of turbulent spectrum. The local wavelet spectrum shows that the physical phenomena such as deformation position in the boundary layer, and the or breakup of eddies are related to the vertical energy-containing eddies exist in a multi-scale form. Moreover, the size of these eddies increases with the measured points moving out of the wall. In the buffer region, the small scale energy-containing eddies with higher frequency are excited. In the outer region, the maximal energy is concentrated in the low-frequency large-scale eddies, and the frequency domain of energy-containing eddies becomes narrower.展开更多
On account of limited knowledge of the breakup of power law liquid film, the process of its disintegration and atomization was studied by using a planar liquid film. A linear stability analysis was adopted to predict ...On account of limited knowledge of the breakup of power law liquid film, the process of its disintegration and atomization was studied by using a planar liquid film. A linear stability analysis was adopted to predict the breakup characteristics of the power law film. The predicting formulas of stripping breakup length and diameter of ligament were put forward presently. Through high-speed photography and laser light sheet illumination,different breakup characteristics of flat power law film under different conditions were derived. The characteristic dimension of breakup regimes were defined and extracted. The effects of several parameters(injection pressure,ambient pressure, nozzle structure and fluid property) on the stripping breakup length and spray angle were investigated. The results revealed that increasing both the velocity of liquid film and the ambient pressure facilitated the breakup of film, reduced the stripping breakup length and enlarged the spray angle in different extents. The comparison between theoretical and experimental results was conducted to validate the feasibility of the linear stability theory.展开更多
文摘采用数值模拟的方法,对在重力作用下微管末端液滴缓慢形成及脱落的动力学过程进行分析和研究。采用有限体积法在轴对称坐标系下求解液滴形成与破碎过程的Navier-Stokes方程,采用VOF(volume of fluid)方法以及基于PLIC(piecewise-linear interface construction)的几何重构方法追踪液滴运动过程的自由表面,捕捉气液界面的演化过程。分析了量纲1液滴最小颈宽以及量纲1液滴高度等相关特征量随相对时间的变化规律,并与实验结果进行了比较。分析了液滴形貌与液滴轴心线上流向速度的变化以及液滴内部涡环形成与湮灭的关系。通过研究轴心线上压力随时间的变化,分析了压力与液滴颈部位置及断裂位置的关系。
文摘基于海洋石油平台系统特征,比较分析了火炬系统的两种热辐射模型,建立了适用于水幕系统的两通量隔热模型.通过实验数据对比,验证了模型的适用性.结果表明,Thornton辐射模型比API RP 521标准中的方法更为合理;雾场特性参数对水幕系统的隔热效果有着很大的影响,水幕透射率随着液滴出口压力的增大而逐渐减小,但影响幅度逐渐减少.基于该模型所得到的实际海洋石油平台的火炬辐射水幕隔热系统的设计证明了该模型具有较好的合理性及较强的工程适用性.
基金supported by the National Natural Science Foundation of China (Nos. 10832001 and10872145)the Program for New Century Excellent Talents in Universities of Education Min-istry of China
文摘The streamwise velocity components at different vertical heights in wall turbulence were measured. Wavelet transform was used to study the turbulent energy spectra, indicating that the global spectrum results from the weighted average of Fourier spectrum based on wavelet scales. W＇avelet transform with more vanishing moments can express the declining of turbulent spectrum. The local wavelet spectrum shows that the physical phenomena such as deformation position in the boundary layer, and the or breakup of eddies are related to the vertical energy-containing eddies exist in a multi-scale form. Moreover, the size of these eddies increases with the measured points moving out of the wall. In the buffer region, the small scale energy-containing eddies with higher frequency are excited. In the outer region, the maximal energy is concentrated in the low-frequency large-scale eddies, and the frequency domain of energy-containing eddies becomes narrower.
基金Supported by the National Natural Science Foundation of China(11172205,11372219,51176137)
文摘On account of limited knowledge of the breakup of power law liquid film, the process of its disintegration and atomization was studied by using a planar liquid film. A linear stability analysis was adopted to predict the breakup characteristics of the power law film. The predicting formulas of stripping breakup length and diameter of ligament were put forward presently. Through high-speed photography and laser light sheet illumination,different breakup characteristics of flat power law film under different conditions were derived. The characteristic dimension of breakup regimes were defined and extracted. The effects of several parameters(injection pressure,ambient pressure, nozzle structure and fluid property) on the stripping breakup length and spray angle were investigated. The results revealed that increasing both the velocity of liquid film and the ambient pressure facilitated the breakup of film, reduced the stripping breakup length and enlarged the spray angle in different extents. The comparison between theoretical and experimental results was conducted to validate the feasibility of the linear stability theory.
