Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetri...Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap,resulting in instability and deterioration of the train’s aerodynamic characteristics,significantly impacting its operational safety.In this study,we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results.We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds.We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties.The findings show that,without crosswinds,a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling,leading to the worst aerodynamic performance.Under crosswind conditions,a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train,resulting in the poorest aerodynamic performance.This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.展开更多
设计能够鉴定小菇属真菌(Mycena sp.)的引物,可准确而快速发现萌发菌分离材料,从而分离小菇属真菌,对提高天麻种子萌发率及天麻产量具有重要现实价值。同时对全面了解小菇属真菌在自然环境中的物种分布情况具有一定生态学意义。根据适...设计能够鉴定小菇属真菌(Mycena sp.)的引物,可准确而快速发现萌发菌分离材料,从而分离小菇属真菌,对提高天麻种子萌发率及天麻产量具有重要现实价值。同时对全面了解小菇属真菌在自然环境中的物种分布情况具有一定生态学意义。根据适用于检测"环境DNA"中某物种的引物设计验证框架,运用Primer Premier v5.0软件,在ITS序列区间内设计了适用于小菇属真菌DNA快速检测的5对引物,并对他们的特异性、灵敏度和实际运用能力进行了评估。其中,特异性较好的4对引物分别为M52-2、M22-3、M11-4和BZZ-5。通过对来自3个门、125个属的125株真菌进行特异性测试,能测出的菌株数量分别为2.4%、6.4%、4.0%和7.2%。灵敏度较好的M22-3和BZZ-5两对引物能检测到小菇属真菌菌丝在土壤中的最小浓度均为0.033%,且能成功从天麻原球茎和种子萌发菌塘土壤样本总DNA中检测出小菇属真菌的存在。结果表明,经过利用2对和多对引物,可在实际运用中快速筛选和发现小菇属真菌。展开更多
The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstruct...The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.展开更多
In this paper, a Euler-Lagrangian particle/fluid film/VOF coupled multiphase flow model is presented. Numerical simulations are conducted, and the rainwater accumulation and flow characteristics over two types of wind...In this paper, a Euler-Lagrangian particle/fluid film/VOF coupled multiphase flow model is presented. Numerical simulations are conducted, and the rainwater accumulation and flow characteristics over two types of windshields are studied based on the presented model. The results show that an uneven water film is formed over the windshield, with rain water accumulation occurring for the concave windshield but not for the convex windshield. At low speeds, the average fluid-film thickness for a concave windshield is larger than that of a convex windshield;however, a minor difference occurs between these two values at high speeds, and a critical velocity is observed for the two types of windshields. When the train velocity is less than the critical velocity, the fluid film at the lower part of the windshield and the train nose flows downward, and beyond the critical velocity, the fluid film over the entire windshield and train nose flows upward.展开更多
基金Projects(52372369,52302447,52388102)supported by the National Natural Science Foundation of ChinaProjects(2022YFB4301201-02,2023YFB4302502-02)supported by the National Key R&D Program of China。
文摘Irregularities in the track and uneven forces acting on the train can cause shifts in the position of the superconducting magnetic levitation train relative to the track during operation.These shifts lead to asymmetries in the flow field structure on both sides of the narrow suspension gap,resulting in instability and deterioration of the train’s aerodynamic characteristics,significantly impacting its operational safety.In this study,we firstly validate the aerodynamic characteristics of the superconducting magnetic levitation system by developing a numerical simulation method based on wind tunnel test results.We then investigate the influence of lateral translation parameters on the train’s aerodynamic performance under conditions both with and without crosswinds.We aim to clarify the evolution mechanism of the flow field characteristics under the coupling effect between the train and the U-shaped track and to identify the most unfavorable operational parameters contributing to the deterioration of the train’s aerodynamic properties.The findings show that,without crosswinds,a lateral translation of 30 mm causes a synchronous resonance phenomenon at the side and bottom gaps of the train-track coupling,leading to the worst aerodynamic performance.Under crosswind conditions,a lateral translation of 40 mm maximizes peak pressure fluctuations and average turbulent kinetic energy around the train,resulting in the poorest aerodynamic performance.This research provides theoretical support for enhancing the operational stability of superconducting magnetic levitation trains.
文摘设计能够鉴定小菇属真菌(Mycena sp.)的引物,可准确而快速发现萌发菌分离材料,从而分离小菇属真菌,对提高天麻种子萌发率及天麻产量具有重要现实价值。同时对全面了解小菇属真菌在自然环境中的物种分布情况具有一定生态学意义。根据适用于检测"环境DNA"中某物种的引物设计验证框架,运用Primer Premier v5.0软件,在ITS序列区间内设计了适用于小菇属真菌DNA快速检测的5对引物,并对他们的特异性、灵敏度和实际运用能力进行了评估。其中,特异性较好的4对引物分别为M52-2、M22-3、M11-4和BZZ-5。通过对来自3个门、125个属的125株真菌进行特异性测试,能测出的菌株数量分别为2.4%、6.4%、4.0%和7.2%。灵敏度较好的M22-3和BZZ-5两对引物能检测到小菇属真菌菌丝在土壤中的最小浓度均为0.033%,且能成功从天麻原球茎和种子萌发菌塘土壤样本总DNA中检测出小菇属真菌的存在。结果表明,经过利用2对和多对引物,可在实际运用中快速筛选和发现小菇属真菌。
基金Project (2016YFB1200602-11) supported by National Key R&D Plan of China
文摘The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.
基金Projects(2016YFB1200602-11,2016YFB1200602-12)supported by the National Key R&D Plan of China
文摘In this paper, a Euler-Lagrangian particle/fluid film/VOF coupled multiphase flow model is presented. Numerical simulations are conducted, and the rainwater accumulation and flow characteristics over two types of windshields are studied based on the presented model. The results show that an uneven water film is formed over the windshield, with rain water accumulation occurring for the concave windshield but not for the convex windshield. At low speeds, the average fluid-film thickness for a concave windshield is larger than that of a convex windshield;however, a minor difference occurs between these two values at high speeds, and a critical velocity is observed for the two types of windshields. When the train velocity is less than the critical velocity, the fluid film at the lower part of the windshield and the train nose flows downward, and beyond the critical velocity, the fluid film over the entire windshield and train nose flows upward.
