利用常规观测资料、加密自动站资料对萍乡市2015年5月的一次区域性大暴雨过程漏报的原因进行了分析,分析表明此次过程漏报原因主要是:1)没有注意到925 h Pa萍乡中部的强温度锋区; 2)忽视了中高层干冷空气扩散南下的影响; 3)误认为低层...利用常规观测资料、加密自动站资料对萍乡市2015年5月的一次区域性大暴雨过程漏报的原因进行了分析,分析表明此次过程漏报原因主要是:1)没有注意到925 h Pa萍乡中部的强温度锋区; 2)忽视了中高层干冷空气扩散南下的影响; 3)误认为低层辐合条件偏弱。利用EC细网格(ECMWF-thin)资料计算此次过程中的一些物理量,对暴雨预报做进一步的诊断分析。分析结果与总结的漏报原因吻合:萍乡市中部低层存在的广义位温的高值中心表明萍乡市中部和北部之间确实存在明显的温度锋区;湿热力平流参数正负中心的交界面证明了萍乡市北部有明显的锋生,锋生是中层干冷空气补充南下叠加在低层高温高湿区上造成的;热力垂直螺旋度和水汽垂直螺旋度的分析则表明低层的水汽和热量辐合条件是较强的。展开更多
The phenomenon of direct-contact condensation,used in steam driven jet injectors,nuclear reactor emergency core cooling systems and direct-contact heat exchangers,was investigated computationally by introducing a ther...The phenomenon of direct-contact condensation,used in steam driven jet injectors,nuclear reactor emergency core cooling systems and direct-contact heat exchangers,was investigated computationally by introducing a thermal equilibrium model for direct-contact condensation of steam in subcooled water.The condensation model presented was a two resistance model which takes care of the heat transfer process on both sides of the interface and uses a variable steam bubble diameter.The injection of supersonic steam jet in subcooled water tank was simulated using the Euler-Euler multiphase flow model of Fluent 6.3 code with the condensation model incorporated. The findings of the computational fluid dynamics（CFD） simulations were compared with the published experimental data and fairly good agreement was observed between the two,thus validating the condensation model.The results of CFD simulations for dimensionless penetration length of steam plume varies from 2.73-7.33,while the condensation heat transfer coefficient varies from 0.75-0.917 MW·（m ^2 ·K）^ -1 for water temperature in the range of 293-343 K.展开更多
We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthi...We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthis study.Using the methods of non-equilibrium thermodynamics,we derive the transport currents correspondingto charge,heat,and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown howtime-dependent magnetic textures give rise to charge and thermal currents even in the absence of external potential andthermal gradients through spin pumping.The presence of dynamical textures also affect the thermodynamic parametersof the system.As an application,we consider the case of a helimagnet.展开更多
Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This pape...Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This paper investigates the dynamic properties of the plasma sheath by using the simplified conventional Burnett(SCB)equations and the Navier-Stokes(NS)equations with the thermochemical non-equilibrium effect.The eleven-species chemical kinetic models are applied to the comparison and there is verification of a dynamic plasma sheath simulation for the first time.After the introduction of vehicle pitching motion,the dynamic results are more consistent with the experimental data than the simulated results when treating it as static state.The plasma sheath characteristic parameters show periodic properties,whose changing period is the same as the pitching motion period.However,because of different velocities of the pitching motion,phase shifts exist in different positions of the vehicle.The enhancement of the rarefied effect weakens the disturbance to the plasma sheath.This research reveals the distribution and regularities of the dynamic plasma sheath.It is significant in solving the ionization blackout problem and the design of the reentry vehicle,and provides reliable data for further research on the dynamic plasma sheath.展开更多
We introduce a pre-hydrodynamic correction to the commonly used Glauber model to bring the random scattering information to the initial condition of the hydrodynamic description for the heavy ion collisions.The result...We introduce a pre-hydrodynamic correction to the commonly used Glauber model to bring the random scattering information to the initial condition of the hydrodynamic description for the heavy ion collisions.The results of this correction obviously shrink the value of the elliptic flow in the medium momentum region and move the corresponding momentum of the maximum v 2 forwards to smaller p T value.These fit the experimental data quite well.This correction implies that the quark-gluon plasma(QGP) has reached the thermal equilibrium when the hydrodynamic expansion starts.Such a conclusion of quick-equilibrium confirms the conclusion that QGP is a strongly interacting system.展开更多
文摘利用常规观测资料、加密自动站资料对萍乡市2015年5月的一次区域性大暴雨过程漏报的原因进行了分析,分析表明此次过程漏报原因主要是:1)没有注意到925 h Pa萍乡中部的强温度锋区; 2)忽视了中高层干冷空气扩散南下的影响; 3)误认为低层辐合条件偏弱。利用EC细网格(ECMWF-thin)资料计算此次过程中的一些物理量,对暴雨预报做进一步的诊断分析。分析结果与总结的漏报原因吻合:萍乡市中部低层存在的广义位温的高值中心表明萍乡市中部和北部之间确实存在明显的温度锋区;湿热力平流参数正负中心的交界面证明了萍乡市北部有明显的锋生,锋生是中层干冷空气补充南下叠加在低层高温高湿区上造成的;热力垂直螺旋度和水汽垂直螺旋度的分析则表明低层的水汽和热量辐合条件是较强的。
文摘The phenomenon of direct-contact condensation,used in steam driven jet injectors,nuclear reactor emergency core cooling systems and direct-contact heat exchangers,was investigated computationally by introducing a thermal equilibrium model for direct-contact condensation of steam in subcooled water.The condensation model presented was a two resistance model which takes care of the heat transfer process on both sides of the interface and uses a variable steam bubble diameter.The injection of supersonic steam jet in subcooled water tank was simulated using the Euler-Euler multiphase flow model of Fluent 6.3 code with the condensation model incorporated. The findings of the computational fluid dynamics（CFD） simulations were compared with the published experimental data and fairly good agreement was observed between the two,thus validating the condensation model.The results of CFD simulations for dimensionless penetration length of steam plume varies from 2.73-7.33,while the condensation heat transfer coefficient varies from 0.75-0.917 MW·（m ^2 ·K）^ -1 for water temperature in the range of 293-343 K.
文摘We study the effect of potential and thermal gradient induced non-equilibrium magnetization in quasi1-d itinerant magnets.A semi-phenomenological theory is employed in conjunction with the drift-diffusion model forthis study.Using the methods of non-equilibrium thermodynamics,we derive the transport currents correspondingto charge,heat,and magnetization flows in the presence of non-equilibrium magnetization textures.It is shown howtime-dependent magnetic textures give rise to charge and thermal currents even in the absence of external potential andthermal gradients through spin pumping.The presence of dynamical textures also affect the thermodynamic parametersof the system.As an application,we consider the case of a helimagnet.
文摘Research on the dynamic properties of a plasma sheath coupled with pitching motion of the vehicle has great significance in solving the problem of communication interruption in the process of vehicle reentry.This paper investigates the dynamic properties of the plasma sheath by using the simplified conventional Burnett(SCB)equations and the Navier-Stokes(NS)equations with the thermochemical non-equilibrium effect.The eleven-species chemical kinetic models are applied to the comparison and there is verification of a dynamic plasma sheath simulation for the first time.After the introduction of vehicle pitching motion,the dynamic results are more consistent with the experimental data than the simulated results when treating it as static state.The plasma sheath characteristic parameters show periodic properties,whose changing period is the same as the pitching motion period.However,because of different velocities of the pitching motion,phase shifts exist in different positions of the vehicle.The enhancement of the rarefied effect weakens the disturbance to the plasma sheath.This research reveals the distribution and regularities of the dynamic plasma sheath.It is significant in solving the ionization blackout problem and the design of the reentry vehicle,and provides reliable data for further research on the dynamic plasma sheath.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10775069,10935001 and 11075075)the Research Fund for the Doctoral Program of Higher Education (Grant No.200802840009)the Priority Academic Program Development of Jiangsu Higher Education Institution
文摘We introduce a pre-hydrodynamic correction to the commonly used Glauber model to bring the random scattering information to the initial condition of the hydrodynamic description for the heavy ion collisions.The results of this correction obviously shrink the value of the elliptic flow in the medium momentum region and move the corresponding momentum of the maximum v 2 forwards to smaller p T value.These fit the experimental data quite well.This correction implies that the quark-gluon plasma(QGP) has reached the thermal equilibrium when the hydrodynamic expansion starts.Such a conclusion of quick-equilibrium confirms the conclusion that QGP is a strongly interacting system.
