[Objective] The research aimed to study the possible mechanism of terrain effect on cold-flow snowstorm.[Method] By using the meso-scale numerical model(WRF),a cold-flow snowstorm weather process in Shandong Peninsula...[Objective] The research aimed to study the possible mechanism of terrain effect on cold-flow snowstorm.[Method] By using the meso-scale numerical model(WRF),a cold-flow snowstorm weather process in Shandong Peninsula was carried out numerical simulation and terrain sensitivity contrast test.The possible reason of terrain effect on falling zone and strength of snowstorm was deeply analyzed from water vapor,thermodynamic field and so on.[Result] The mountain terrain in Shandong Peninsula had great influences on falling zone and strength of cold-flow snowstorm.The strength of snowstorm obviously increased,and the snowfall center obviously moved northward.The main reason was that terrain caused the low-level wind field convergence and vertical movement in the troposphere strengthened.Then,the spatial distribution of water vapor and snow water content in the cold-flow snowstorm process obviously changed.So,the whole snowstorm process was affected.[Conclusion] The mountain terrain in Shandong Peninsula was the important element which needed to be focused on considering in the forecast analysis of cold-flow snowstorm weather process.展开更多
Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ...Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.展开更多
总结了油气田冷放空设计的原则和依据,以及放空气体大气扩散的主要影响因素。基于冷放空的本质和流体的物性,引用了射流理论的密度弗劳德数定义式来描述放空气扩散运动的特征。分别介绍了API Standard 521和流体动力学中放空气浓度和扩...总结了油气田冷放空设计的原则和依据,以及放空气体大气扩散的主要影响因素。基于冷放空的本质和流体的物性,引用了射流理论的密度弗劳德数定义式来描述放空气扩散运动的特征。分别介绍了API Standard 521和流体动力学中放空气浓度和扩散距离的关系式,阐述了确定冷放空管尺寸和高度的方法。介绍了雷诺数判据和密度弗劳德数定义式在扩散模拟分析中的应用。基于对理查逊数用于Pasquill大气稳定度的研究成果,提出了使用CFD软件模拟放空气扩散时大气环境的模拟方法。最后通过软件仿真计算结果对比了放空口水平朝向和垂直朝向对扩散的不同影响。展开更多
基金Supported by Special Item of Public Welfare Industry (Meteorology)Science Research (GYHY201106006)Special Item of Forecaster of China Meteorological Administration (CMATG2007Y08)Key Topics of Shandong Meteorological Bureau (2010sdqxz10)
文摘[Objective] The research aimed to study the possible mechanism of terrain effect on cold-flow snowstorm.[Method] By using the meso-scale numerical model(WRF),a cold-flow snowstorm weather process in Shandong Peninsula was carried out numerical simulation and terrain sensitivity contrast test.The possible reason of terrain effect on falling zone and strength of snowstorm was deeply analyzed from water vapor,thermodynamic field and so on.[Result] The mountain terrain in Shandong Peninsula had great influences on falling zone and strength of cold-flow snowstorm.The strength of snowstorm obviously increased,and the snowfall center obviously moved northward.The main reason was that terrain caused the low-level wind field convergence and vertical movement in the troposphere strengthened.Then,the spatial distribution of water vapor and snow water content in the cold-flow snowstorm process obviously changed.So,the whole snowstorm process was affected.[Conclusion] The mountain terrain in Shandong Peninsula was the important element which needed to be focused on considering in the forecast analysis of cold-flow snowstorm weather process.
基金supported by the National Natural Science Foundation of China(No.12002102)。
文摘Cold-flow experiments on planar Expansion Deflection(ED)nozzle flows are conducted under a simulated startup-shutdown process of rocket motors.The purpose is to investigate the flow and performance characteristics in ED nozzles,capture the behavior of shock flapping,and explore asymmetric flow dynamics utilizing a symmetric nozzle.A total pressure condition,characterized by rapid rise followed by a slow fall,is employed to simulate the continuous startup and shutdown processes.The schlieren imaging technique and high-frequency pressure transducers are employed to obtain the flow information.The experimental results indicate that the flow characteristics differ between the startup and shutdown processes with a hysteresis observed in the nozzle wake mode transition.During the startup process,the shock waves are pushed outward of the nozzle,while during the shutdown process,the flow propagates inward dominated by Mach stems.Counterintuitive results are demonstrated,namely,the mode transition is not the cause of the sudden thrust decrease,and the moment of maximum thrust does not coincide with the moment of maximum total pressure.During the operation of the nozzle,two stages of shock wave flapping occur,accompanied by significant wall pressure oscillations.These oscillation frequencies are demonstrated to be related to the inherent acoustic frequencies of the test chamber.An improved pressure ratio method is proposed to predict the position of the shock oscillation separation point.The prediction results revealed the shock behavior during the flapping process.
文摘总结了油气田冷放空设计的原则和依据,以及放空气体大气扩散的主要影响因素。基于冷放空的本质和流体的物性,引用了射流理论的密度弗劳德数定义式来描述放空气扩散运动的特征。分别介绍了API Standard 521和流体动力学中放空气浓度和扩散距离的关系式,阐述了确定冷放空管尺寸和高度的方法。介绍了雷诺数判据和密度弗劳德数定义式在扩散模拟分析中的应用。基于对理查逊数用于Pasquill大气稳定度的研究成果,提出了使用CFD软件模拟放空气扩散时大气环境的模拟方法。最后通过软件仿真计算结果对比了放空口水平朝向和垂直朝向对扩散的不同影响。
