Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dyna...Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dynamics and lattice Boltzmalm method （LBM）. By taking the effect of molecule force in droplet and the wall surface on liquid film into account, the changing law of contact angle with different surface tensions was analyzed on glass and aluminum foil surfaces. Compared with experimental results, the standard deviation by using LBM is less than 0.5°, which validates the feasibility of LBM simulation on the dynamic process of liquid film spreading. In addition, oscillations are discovered both at the initial and end phases. The phenomenon of retraction is also found and the maximum retraction angle is 7.58°. The obtained result shows that the retraction is proved to be correlative with precursor film by tracking the volume change of liquid film contour. Furthermore, non-dimensional coefficient 2 is introduced to measure the liquid film retraction capacity.展开更多
A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combin...A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.展开更多
Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct...Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.展开更多
The submerged propeller is an efficient diving mix device,which is applicable for oxidation ditch treatment in industry,city and village wastewater-treatment plant. The impeller structure and reasonable rotating speed...The submerged propeller is an efficient diving mix device,which is applicable for oxidation ditch treatment in industry,city and village wastewater-treatment plant. The impeller structure and reasonable rotating speed are important factors that determine flow field distribution and energy conversion efficiency. So it is necessary to use modern design methods to develop new kinds of high efficiency submerged propellers,and research the flow field characteristics of submerged propellers. On the basis of the existing form drawing,three-dimensional model of submerged propellers and unstructured tetrahedral mesh were generated. Based on Navier- Stokes equations and standard k- ε turbulence model,the flow was simulated by using a simple algorithm. Through changing some design parameters of propellers,the corresponding numerical simulation results reveal that for the same impeller diameter and service area of submerged propellers,the power consumption could be reduced effectively by optimizing blade mounting angle,which can determine the best blade mounting angle and most suitable rotational speed under given conditions. The study can provide theoretical and project guidance for submerged propellers design.展开更多
应用Realizable k-ε湍流模型和VOF(Volume of Fraction)两相流模型对某压力旋流喷嘴进行数值研究,分析了旋流室锥角、旋流孔角度及喷嘴入口压力变化对雾化锥角、雾化粒径及分布、液滴速度分布等参数的影响。结果表明:雾化锥角受旋流室...应用Realizable k-ε湍流模型和VOF(Volume of Fraction)两相流模型对某压力旋流喷嘴进行数值研究,分析了旋流室锥角、旋流孔角度及喷嘴入口压力变化对雾化锥角、雾化粒径及分布、液滴速度分布等参数的影响。结果表明:雾化锥角受旋流室锥角的影响幅度随压力增大而减小,雾化粒径及分布受旋流室锥角影响不明显,当旋流室锥角为90°时雾化范围广且雾化稳定性好;雾化锥角随旋流孔角度增大先增后减,当角度为45°时雾化锥角最大,平均粒径及其分布更佳;当喷嘴入口压力逐渐增大时,雾化锥角与雾化粒径均逐渐减小,液滴速度区间逐渐缩小,当入口压力达到0.4 MPa时,Sauter粒径及液滴粒径分布趋于稳定,液滴速度分布最为集中。展开更多
失速工况下,气液两相流离心泵的内部流动极为复杂。为探究不同进口含气率对离心泵失速工况流动特性的影响,该研究基于欧拉-欧拉非均相流模型和SST k-ω湍流模型,分析了进口含气率对离心泵性能的影响规律。纯水条件下,基于性能曲线和内...失速工况下,气液两相流离心泵的内部流动极为复杂。为探究不同进口含气率对离心泵失速工况流动特性的影响,该研究基于欧拉-欧拉非均相流模型和SST k-ω湍流模型,分析了进口含气率对离心泵性能的影响规律。纯水条件下,基于性能曲线和内部流动特性分析可知,0.70倍设计流量(0.70Q_(d))和0.65Q_(d)是失速发展阶段的典型工况,流场的周向均匀性存在不同程度的破坏。2个典型失速工况下,随着进口含气率的增加,泵的性能下降但下降幅度相比设计工况和深度失速工况小,气相主要附着在叶片压力侧前缘附近且附着面积逐渐增大,失速流道压力侧前缘的相对速度角增大,流动方向整体向吸力侧偏移,使得吸力侧前缘冲角减小,抑制了吸力侧前缘分离涡和中间位置漩涡的融合,进而抑制了失速的发生。引入流量变异系数(coefficient of variance,CV)定量分析流场的周向均匀性,随着流场改善,CV值逐渐减小,当模型泵处于失速初生点时,CV值位于1.38%~3.69%。少量气体加入使得失速发展阶段离心泵性能下降幅度减小且抑制失速发生。研究结果可为拓宽离心泵的高效区和提高安全稳定运行提供参考。展开更多
基金Project(U1261107)supported by the National Natural Science Foundation of China
文摘Combined with the kinetic model of liquid film spreading, a new numerical method of solid-liquid-gas three-phase flow was developed for the moving of contact line, which was a hybrid method of computational fluid dynamics and lattice Boltzmalm method （LBM）. By taking the effect of molecule force in droplet and the wall surface on liquid film into account, the changing law of contact angle with different surface tensions was analyzed on glass and aluminum foil surfaces. Compared with experimental results, the standard deviation by using LBM is less than 0.5°, which validates the feasibility of LBM simulation on the dynamic process of liquid film spreading. In addition, oscillations are discovered both at the initial and end phases. The phenomenon of retraction is also found and the maximum retraction angle is 7.58°. The obtained result shows that the retraction is proved to be correlative with precursor film by tracking the volume change of liquid film contour. Furthermore, non-dimensional coefficient 2 is introduced to measure the liquid film retraction capacity.
文摘A terminal ballistic analysis of the effects of 7.62 mm × 51 AP P80 rounds on inclined high-strength armor steel plates is the focus of the presented study.The findings of an instrumented ballistic testing combined with 3D advanced numerical simulations performed using the IMPETUS Afea? software yielded the conclusions.The experimental verification proved that slight differences in the pitch-andyaw angles of a projectile upon an impact caused different damage types to the projectile’s core.The residual velocities predicted numerically were close to the experimental values and the calculated core deviations were in satisfactory agreement with the experimental results.An extended matrix of the core deviation angles with combinations of pitch-and-yaw upon impact angles was subsequently built on the basis of the numerical study.The presented experimental and numerical investigation examined thoroughly the influence of the initial pitch and yaw angles on the after-perforation projectile’s performance.
基金Project(HEUCF110707)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(E201216)supported by Heilongjiang Natural Science Fund,China
文摘Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.
基金The support of College of Energy and Electrical Engineering,Hohai University,ChinaNational Natural Science Foundation of China ( No.51106042)
文摘The submerged propeller is an efficient diving mix device,which is applicable for oxidation ditch treatment in industry,city and village wastewater-treatment plant. The impeller structure and reasonable rotating speed are important factors that determine flow field distribution and energy conversion efficiency. So it is necessary to use modern design methods to develop new kinds of high efficiency submerged propellers,and research the flow field characteristics of submerged propellers. On the basis of the existing form drawing,three-dimensional model of submerged propellers and unstructured tetrahedral mesh were generated. Based on Navier- Stokes equations and standard k- ε turbulence model,the flow was simulated by using a simple algorithm. Through changing some design parameters of propellers,the corresponding numerical simulation results reveal that for the same impeller diameter and service area of submerged propellers,the power consumption could be reduced effectively by optimizing blade mounting angle,which can determine the best blade mounting angle and most suitable rotational speed under given conditions. The study can provide theoretical and project guidance for submerged propellers design.
文摘应用Realizable k-ε湍流模型和VOF(Volume of Fraction)两相流模型对某压力旋流喷嘴进行数值研究,分析了旋流室锥角、旋流孔角度及喷嘴入口压力变化对雾化锥角、雾化粒径及分布、液滴速度分布等参数的影响。结果表明:雾化锥角受旋流室锥角的影响幅度随压力增大而减小,雾化粒径及分布受旋流室锥角影响不明显,当旋流室锥角为90°时雾化范围广且雾化稳定性好;雾化锥角随旋流孔角度增大先增后减,当角度为45°时雾化锥角最大,平均粒径及其分布更佳;当喷嘴入口压力逐渐增大时,雾化锥角与雾化粒径均逐渐减小,液滴速度区间逐渐缩小,当入口压力达到0.4 MPa时,Sauter粒径及液滴粒径分布趋于稳定,液滴速度分布最为集中。
文摘失速工况下,气液两相流离心泵的内部流动极为复杂。为探究不同进口含气率对离心泵失速工况流动特性的影响,该研究基于欧拉-欧拉非均相流模型和SST k-ω湍流模型,分析了进口含气率对离心泵性能的影响规律。纯水条件下,基于性能曲线和内部流动特性分析可知,0.70倍设计流量(0.70Q_(d))和0.65Q_(d)是失速发展阶段的典型工况,流场的周向均匀性存在不同程度的破坏。2个典型失速工况下,随着进口含气率的增加,泵的性能下降但下降幅度相比设计工况和深度失速工况小,气相主要附着在叶片压力侧前缘附近且附着面积逐渐增大,失速流道压力侧前缘的相对速度角增大,流动方向整体向吸力侧偏移,使得吸力侧前缘冲角减小,抑制了吸力侧前缘分离涡和中间位置漩涡的融合,进而抑制了失速的发生。引入流量变异系数(coefficient of variance,CV)定量分析流场的周向均匀性,随着流场改善,CV值逐渐减小,当模型泵处于失速初生点时,CV值位于1.38%~3.69%。少量气体加入使得失速发展阶段离心泵性能下降幅度减小且抑制失速发生。研究结果可为拓宽离心泵的高效区和提高安全稳定运行提供参考。
