By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow...By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.展开更多
In this study,direct numerical simulations were conducted to investigate the compressible flow around a circular cylinder near a heated wall at a Reynolds number(Re)of 500 and a Mach number(Ma)of 0.4.The heating ratio...In this study,direct numerical simulations were conducted to investigate the compressible flow around a circular cylinder near a heated wall at a Reynolds number(Re)of 500 and a Mach number(Ma)of 0.4.The heating ratio T^(*)ranging from 1.0 to 1.6 represents the different situations of a heated wall,whereas the gap ratio ranges from 0.3 to 1.0.This study analyzed the impact of heating effect and wall proximity on flow characteristics and aerodynamic forces.The results indicated that the stability of the flow was enhanced as the gap ratio decreased or the heating ratio increased.Through the calculation of enstrophy,it was found that the strength of shedding vortices weakens with a decrease in gap ratio or an increase in heating ratio.Furthermore,the mean drag coefficient decreases as the heating ratio increases or the gap ratio decreases.In contrast,the mean lift coefficient initially decreases and then increases as the gap ratio decreases.Finally,the drag reduction mechanism was analyzed by examining the pressure distribution on the surface of the cylinder.展开更多
In this paper,the large eddy simulation(LES)method is used to calculate Reynolds numbers the range in the range of 3000–30000(based on the diameter of the hemisphere D),and then the statistical analysis method is use...In this paper,the large eddy simulation(LES)method is used to calculate Reynolds numbers the range in the range of 3000–30000(based on the diameter of the hemisphere D),and then the statistical analysis method is used to study the influence of Re on the characteristics of the flow field around the rough hemisphere and the evolution law of the tail vortex.The effect of the Reynolds number on the structure of the rough hemisphere flow field and the evolution of vortex structure is studied by vorticity distribution,POD method,and correlation analysis.It can be observed that with the increase of Reynolds number,the shear in the recirculating region of the rough hemisphere is enhanced,the large-scale structure is reduced,the small-scale structure is increased,and the angle between the hairpin vortex and the wall is reduced.λ_(ci)vortex identification and the Q-criterion are used to capture the evolution of a periodic vortex structure.Q-criterion gives the three-dimensional vortex structure behind the hemispherical flow.It is found that the horseshoe vortex and arch vortex generated by the incoming flow after passing through the hemisphere will interact with the wall surface to form a hairpin vortex,and the hairpin vortex structure will continue to evolve downstream to form a new vortex structure.展开更多
Given the increasing incidence of neurodegenerative disease(ND),recent research efforts have intensified the search for curative treatments.Despite significant research,however,existing therapeutic options for ND can ...Given the increasing incidence of neurodegenerative disease(ND),recent research efforts have intensified the search for curative treatments.Despite significant research,however,existing therapeutic options for ND can only slow down the progression of the disease,but not provide a cure.Light therapy(LT)has been used to treat some mental and sleep disorders.This review illustrates recent studies of the use of LT in patients with ND and highlights its potential for clinical applications.The literature was collected from PubMed through June 2020.Selected studies were primarily English articles or articles that could be obtained with English abstracts and Chinese main text.Articles were not limited by type.Additional potential publications were also identified from the bibliographies of identified articles and the authors’reference libraries.The identified literature suggests that LT is a safe and convenient physical method of treatment.It may alleviate sleep disorders,depression,cognitive function,and other clinical symptoms.However,some studies have reported limited or no effects.Therefore,LT represents an attractive therapeutic approach for further investigation in ND.LT is an effective physical form of therapy and a new direction for research into treatments for ND.However,it requires further animal experiments to elucidate mechanisms of action and large,double-blind,randomized,and controlled trials to explore true efficacy in patients with ND.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 50679061, 50709025,50749031)
文摘By choosing a PVC slice to simulate flexible vegetation, we carried out experiments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter （micro ADV） was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter representing the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.12032016,12372277).
文摘In this study,direct numerical simulations were conducted to investigate the compressible flow around a circular cylinder near a heated wall at a Reynolds number(Re)of 500 and a Mach number(Ma)of 0.4.The heating ratio T^(*)ranging from 1.0 to 1.6 represents the different situations of a heated wall,whereas the gap ratio ranges from 0.3 to 1.0.This study analyzed the impact of heating effect and wall proximity on flow characteristics and aerodynamic forces.The results indicated that the stability of the flow was enhanced as the gap ratio decreased or the heating ratio increased.Through the calculation of enstrophy,it was found that the strength of shedding vortices weakens with a decrease in gap ratio or an increase in heating ratio.Furthermore,the mean drag coefficient decreases as the heating ratio increases or the gap ratio decreases.In contrast,the mean lift coefficient initially decreases and then increases as the gap ratio decreases.Finally,the drag reduction mechanism was analyzed by examining the pressure distribution on the surface of the cylinder.
基金supported by the National Natural Science Foundation of China(Grant No.91952102).
文摘In this paper,the large eddy simulation(LES)method is used to calculate Reynolds numbers the range in the range of 3000–30000(based on the diameter of the hemisphere D),and then the statistical analysis method is used to study the influence of Re on the characteristics of the flow field around the rough hemisphere and the evolution law of the tail vortex.The effect of the Reynolds number on the structure of the rough hemisphere flow field and the evolution of vortex structure is studied by vorticity distribution,POD method,and correlation analysis.It can be observed that with the increase of Reynolds number,the shear in the recirculating region of the rough hemisphere is enhanced,the large-scale structure is reduced,the small-scale structure is increased,and the angle between the hairpin vortex and the wall is reduced.λ_(ci)vortex identification and the Q-criterion are used to capture the evolution of a periodic vortex structure.Q-criterion gives the three-dimensional vortex structure behind the hemispherical flow.It is found that the horseshoe vortex and arch vortex generated by the incoming flow after passing through the hemisphere will interact with the wall surface to form a hairpin vortex,and the hairpin vortex structure will continue to evolve downstream to form a new vortex structure.
基金National Natural Science Foundation of China(Nos.81908217,81801253 and 91649114)Natural Science foundation of Jiangsu Higher Education Institutions of China(No.19KJB180007)+3 种基金Jiangsu Provincial Social Development Projects(Nos.BE2018658,BE2017653)Jiangsu Provincial Medical Key Discipline Project(No.ZDXKB2016022)Jiangsu Province Postgraduate Training Innovation Project(No.KYCX182545)Suzhou Clinical Research Center of Neurological Disease(No.Szzx201503)。
文摘Given the increasing incidence of neurodegenerative disease(ND),recent research efforts have intensified the search for curative treatments.Despite significant research,however,existing therapeutic options for ND can only slow down the progression of the disease,but not provide a cure.Light therapy(LT)has been used to treat some mental and sleep disorders.This review illustrates recent studies of the use of LT in patients with ND and highlights its potential for clinical applications.The literature was collected from PubMed through June 2020.Selected studies were primarily English articles or articles that could be obtained with English abstracts and Chinese main text.Articles were not limited by type.Additional potential publications were also identified from the bibliographies of identified articles and the authors’reference libraries.The identified literature suggests that LT is a safe and convenient physical method of treatment.It may alleviate sleep disorders,depression,cognitive function,and other clinical symptoms.However,some studies have reported limited or no effects.Therefore,LT represents an attractive therapeutic approach for further investigation in ND.LT is an effective physical form of therapy and a new direction for research into treatments for ND.However,it requires further animal experiments to elucidate mechanisms of action and large,double-blind,randomized,and controlled trials to explore true efficacy in patients with ND.
