The subgrid-scale effects on particle motion were investigated in forced isotropic turbulence by DNS and priorLES methods.In the DNS field,the importance of Kolmogorov scaling to preferential accumulation was validate...The subgrid-scale effects on particle motion were investigated in forced isotropic turbulence by DNS and priorLES methods.In the DNS field,the importance of Kolmogorov scaling to preferential accumulation was validated by comparing the radial distribution functions under various particle Stokes numbers.The prior-LES fields were generated by filtering the DNS data.The subgrid-scale Stokes number(StSGS)is a useful tool for determining the effects of subgrid-scale eddies on particle motion.The subgrid-scale eddies tend to accumulate particles with StSGSb 1 and disperse particles with 1 b StSGSb 10.For particles with StSGS?1,the effects of subgrid-scale eddies on particle motion can be neglected.In order to restore the subgrid-scale effects,the Langevin-type stochastic model with optimized parameters was adopted in this study.This model is effective for the particles with StSGS N 1 while has an adverse impact on the particles with StSGSb 1.The results show that the Langevin-type stochastic model tends to smooth the particle distribution in the isotropic turbulence.展开更多
The micro- and macro-time scales in two-phase turbulent channel flows are investigated using the direct nu- merical simulation and the Lagrangian particle trajectory methods for the fluid- and the particle-phases, res...The micro- and macro-time scales in two-phase turbulent channel flows are investigated using the direct nu- merical simulation and the Lagrangian particle trajectory methods for the fluid- and the particle-phases, respectively. Lagrangian and Eulerian time scales of both phases are cal- culated using velocity correlation functions. Due to flow anisotropy, micro-time scales are not the same with the theo- retical estimations in large Reynolds number （isotropic） tur- bulence. Lagrangian macro-time scales of particle-phase and of fluid-phase seen by particles are both dependent on particle Stokes number. The fluid-phase Lagrangian inte- gral time scales increase with distance from the wall, longer than those time scales seen by particles. The Eulerian inte- gral macro-time scales increase in near-wall regions but de- crease in out-layer regions. The moving Eulerian time scales are also investigated and compared with Lagrangian integral time scales, and in good agreement with previous measure- ments and numerical predictions. For the fluid particles the micro Eulerian time scales are longer than the Lagrangian ones in the near wall regions, while away from the walls the micro Lagrangian time scales are longer. The Lagrangian integral time scales are longer than the Eulerian ones. The results are useful for further understanding two-phase flow physics and especially for constructing accurate prediction models of inertial particle dispersion.展开更多
目的:探究上肢运动功能Fugl-Meyer评定法(fugl-meyer assessment of upper extremity,FMA-UE)、简易上肢功能评定量表(simple test for evaluating hand function,STEF)、上肢功能测试量表(testévaluant les membres supérieu...目的:探究上肢运动功能Fugl-Meyer评定法(fugl-meyer assessment of upper extremity,FMA-UE)、简易上肢功能评定量表(simple test for evaluating hand function,STEF)、上肢功能测试量表(testévaluant les membres supérieurs des personnes agées,TEMPA)的相关性,观察三者应用于不同程度脑卒中患者时是否出现天花板效应或地板效应,并比较3个量表的反应性,为临床中量表选择提供指导。方法:对216例脑卒中患者使用FMA-UE、STEF、TEMPA进行上肢功能的评估,采用Spearman法分析三个量表的相关性,计算取得接近最大/最小分值人数所占总人数的比例,观察是否出现天花板效应或地板效应。另选取20例处于亚急性期的患者进行常规上肢康复训练,2周后再次用TEMPA量表、FMA-UE、STEF进行上肢功能评估,分别观察三个量表的反应性。结果:FMA-UE与STEF的相关系数r=0.767,与TEMPA各维度的相关系数r=0.559~0.848;STEF与TEMPA各维度的相关系数为r=0.840~0.908。FMA-UE在上肢轻度障碍患者中表现出天花板效应,STEF在上肢中度障碍患者中表现出明显地板效应、在上肢重度障碍患者中全部患者得分为0分,TEMPA量表未表现出天花板效应或地板效应。三个量表的反应性均较好,其中效应尺度(ES):FMA-UE>STEF>TEMPA任务分析维度>TEMPA功能评分维度,标准化反应均数(SRM)、基于中位数的效应尺度(MES):FMA-UE>TEMPA任务分析维度>STEF>TEMPA功能评分维度。结论:三个上肢功能评估量表之间具有高度相关性且反应性均较好。但FMA-UE在上肢轻度障碍患者中出现天花板效应,STEF只适用于上肢轻度障碍患者,TEMPA量表未发现天花板效应或地板效应,可应用范围较广。展开更多
Oscillatory turbulent flow over a flat plate was studied by using large eddy simulation (LES) and Reynolds-average Navier-Stokes (RANS) methods. A dynamic subgrid-scale model was employed in LES and Saffman's tur...Oscillatory turbulent flow over a flat plate was studied by using large eddy simulation (LES) and Reynolds-average Navier-Stokes (RANS) methods. A dynamic subgrid-scale model was employed in LES and Saffman's turbulence model was used in RANS. The flow behaviors were discussed for the accelerating and decelerating phases during the oscillating cycle. The friction force on the wall and its phase shift from laminar to turbulent regime were also investigated for different Reynolds numbers. (Edited author abstract) 11 Refs.展开更多
基金Supported by the National Natural Science Foundation of China(51761125011).
文摘The subgrid-scale effects on particle motion were investigated in forced isotropic turbulence by DNS and priorLES methods.In the DNS field,the importance of Kolmogorov scaling to preferential accumulation was validated by comparing the radial distribution functions under various particle Stokes numbers.The prior-LES fields were generated by filtering the DNS data.The subgrid-scale Stokes number(StSGS)is a useful tool for determining the effects of subgrid-scale eddies on particle motion.The subgrid-scale eddies tend to accumulate particles with StSGSb 1 and disperse particles with 1 b StSGSb 10.For particles with StSGS?1,the effects of subgrid-scale eddies on particle motion can be neglected.In order to restore the subgrid-scale effects,the Langevin-type stochastic model with optimized parameters was adopted in this study.This model is effective for the particles with StSGS N 1 while has an adverse impact on the particles with StSGSb 1.The results show that the Langevin-type stochastic model tends to smooth the particle distribution in the isotropic turbulence.
基金supported by the National Natural Science Foundation of China (11132005 and 50706021)
文摘The micro- and macro-time scales in two-phase turbulent channel flows are investigated using the direct nu- merical simulation and the Lagrangian particle trajectory methods for the fluid- and the particle-phases, respectively. Lagrangian and Eulerian time scales of both phases are cal- culated using velocity correlation functions. Due to flow anisotropy, micro-time scales are not the same with the theo- retical estimations in large Reynolds number （isotropic） tur- bulence. Lagrangian macro-time scales of particle-phase and of fluid-phase seen by particles are both dependent on particle Stokes number. The fluid-phase Lagrangian inte- gral time scales increase with distance from the wall, longer than those time scales seen by particles. The Eulerian inte- gral macro-time scales increase in near-wall regions but de- crease in out-layer regions. The moving Eulerian time scales are also investigated and compared with Lagrangian integral time scales, and in good agreement with previous measure- ments and numerical predictions. For the fluid particles the micro Eulerian time scales are longer than the Lagrangian ones in the near wall regions, while away from the walls the micro Lagrangian time scales are longer. The Lagrangian integral time scales are longer than the Eulerian ones. The results are useful for further understanding two-phase flow physics and especially for constructing accurate prediction models of inertial particle dispersion.
文摘目的:探究上肢运动功能Fugl-Meyer评定法(fugl-meyer assessment of upper extremity,FMA-UE)、简易上肢功能评定量表(simple test for evaluating hand function,STEF)、上肢功能测试量表(testévaluant les membres supérieurs des personnes agées,TEMPA)的相关性,观察三者应用于不同程度脑卒中患者时是否出现天花板效应或地板效应,并比较3个量表的反应性,为临床中量表选择提供指导。方法:对216例脑卒中患者使用FMA-UE、STEF、TEMPA进行上肢功能的评估,采用Spearman法分析三个量表的相关性,计算取得接近最大/最小分值人数所占总人数的比例,观察是否出现天花板效应或地板效应。另选取20例处于亚急性期的患者进行常规上肢康复训练,2周后再次用TEMPA量表、FMA-UE、STEF进行上肢功能评估,分别观察三个量表的反应性。结果:FMA-UE与STEF的相关系数r=0.767,与TEMPA各维度的相关系数r=0.559~0.848;STEF与TEMPA各维度的相关系数为r=0.840~0.908。FMA-UE在上肢轻度障碍患者中表现出天花板效应,STEF在上肢中度障碍患者中表现出明显地板效应、在上肢重度障碍患者中全部患者得分为0分,TEMPA量表未表现出天花板效应或地板效应。三个量表的反应性均较好,其中效应尺度(ES):FMA-UE>STEF>TEMPA任务分析维度>TEMPA功能评分维度,标准化反应均数(SRM)、基于中位数的效应尺度(MES):FMA-UE>TEMPA任务分析维度>STEF>TEMPA功能评分维度。结论:三个上肢功能评估量表之间具有高度相关性且反应性均较好。但FMA-UE在上肢轻度障碍患者中出现天花板效应,STEF只适用于上肢轻度障碍患者,TEMPA量表未发现天花板效应或地板效应,可应用范围较广。
基金The project supported by the Youngster Funding of Academia Sinica and by the National Natural Science Foundation of China
文摘Oscillatory turbulent flow over a flat plate was studied by using large eddy simulation (LES) and Reynolds-average Navier-Stokes (RANS) methods. A dynamic subgrid-scale model was employed in LES and Saffman's turbulence model was used in RANS. The flow behaviors were discussed for the accelerating and decelerating phases during the oscillating cycle. The friction force on the wall and its phase shift from laminar to turbulent regime were also investigated for different Reynolds numbers. (Edited author abstract) 11 Refs.
