The present article is focused on modelling of flow and heat transfer behaviour of Cu-water nanofluid in a confined slot jet impingement on hot moving plate.Different parameters such as various moving plate velocities...The present article is focused on modelling of flow and heat transfer behaviour of Cu-water nanofluid in a confined slot jet impingement on hot moving plate.Different parameters such as various moving plate velocities,nanoparticles at various concentrations,variation in turbulent Reynolds number and jet nozzle to plate distance have been considered to study the flow field and convective heat transfer performance of the system.Results of distribution of local and average Nusselt number and skin friction coefficients at the plate surface are shown to elucidate the heat transfer and fluid flow process.Qualitative analysis of both stream function and isotherm contours are carried out to perceive the flow pattern and heat transfer mechanism due to moving plate.The results revealed that average Nusselt number significantly rises with plate velocity in addition with jet inlet Reynolds number.Correlations of the average Nusselt numbers are presented.展开更多
The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distan...The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field hut the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.展开更多
We apply the heat jet approach to realize atomic simulations at finite temperature for a Frenkel–Kontorova chain with moving dislocation. This approach accurately and efficiently controls the system temperature by in...We apply the heat jet approach to realize atomic simulations at finite temperature for a Frenkel–Kontorova chain with moving dislocation. This approach accurately and efficiently controls the system temperature by injecting thermal fluctuations into the system from its boundaries, without modifying the governing equations for the interior domain. This guarantees the dislocation propagating in the atomic chain without nonphysical damping or deformation. In contrast to the non-equilibrium Nosé–Hoover heat bath, the heat jet approach efficiently suppresses boundary reflections while the moving dislocation and interior waves pass across the boundary. The system automatically returns back to the equilibrium state after all non-thermal motions pass away. We further apply this approach to study the impact of periodic potential and temperature field on the velocity of moving dislocation.展开更多
The effects of synthetic jet control on unsteady dynamic stall over rotor airfoil are investigated numerically. A moving-embedded grid method and an Unsteady Reynolds Averaged Navier-Stokes（URANS） solver coupled wit...The effects of synthetic jet control on unsteady dynamic stall over rotor airfoil are investigated numerically. A moving-embedded grid method and an Unsteady Reynolds Averaged Navier-Stokes（URANS） solver coupled with k-x Shear Stress Transport（SST） turbulence model are established for predicting the complex flowfields of oscillatory airfoil under jet control. Additionally, a velocity boundary condition modeled by sinusoidal function has been developed to fulfill the perturbation effect of periodic jet. The validity of present CFD method is evaluated by comparisons of the calculated results of baseline dynamic stall case for rotor airfoil and jet control case for VR-7 B airfoil with experimental data. Then, parametric analyses are conducted emphatically for an OA212 rotor airfoil to investigate the effects of jet control parameters（jet location, dimensionless frequency, momentum coefficient, jet angle, jet type and dual-jet） on dynamic stall characteristics of rotor airfoil. It is demonstrated by the calculated results that efficiency of jet control could be improved with specific momentum coefficient and jet angle when the jet is located near separation point of rotor airfoil. Furthermore, the dual-jet could improve control efficiency more obviously on dynamic stall of rotor airfoil with respect to the unique jet, and the influence laws of dual-jet＇s angles and momentum coefficients on control effects are similar to those of the unique jet. Finally,unsteady aerodynamic characteristics of rotor via synthetic jet which is located on the upper surface of rotor blade in forward flight are calculated, and as a result, the aerodynamic characteristics of rotor are improved compared with the baseline. The results indicate that synthetic jet has the capability in improving aerodynamic characteristics of rotor.展开更多
对于环流特征相似的寒潮过程,其爆发的方式、产生的天气和影响的区域基本相似,但个别寒潮过程却存在较大的差异,造成预报上的误判。针对此类特例,基于常规气象观测资料,自动站观测资料和NCEP逐6 h 1°×1°再分析资料,应用...对于环流特征相似的寒潮过程,其爆发的方式、产生的天气和影响的区域基本相似,但个别寒潮过程却存在较大的差异,造成预报上的误判。针对此类特例,基于常规气象观测资料,自动站观测资料和NCEP逐6 h 1°×1°再分析资料,应用天气学分析和诊断方法,对2014年4月24日（过程1）和5月1日（过程2）2次寒潮天气过程的环流、系统和爆发的动力、热力学机制等进行对比分析。结果表明：2次过程北半球中高纬500 h Pa环流形势均具有两脊一槽的环流特征。寒潮区域升温明显,前期平均温度分别比历史同期偏高1.0-7.3℃和0.1-10.7℃,500 h Pa冷槽和强锋区均在新疆北部堆积、爆发南侵;2次过程在爆发方式和成因上存在着较大的差异,过程1中促使寒潮爆发流场为横槽转竖,槽前疏散结构和正涡度平流使低槽切断出低涡并东南移,冷平流中心移至槽前,横槽转竖寒潮爆发。过程2为低槽东移,冷槽移过阿尔泰山和蒙古高原加深东移,冷空气入侵内蒙古,寒潮爆发。虽然2次过程均造成了全区范围的强降温,但由于上述影响方式和成因的不同,使得大风、沙尘暴和降水呈现出不同的影响特点。寒潮过程中大风和沙尘暴的分布除与冷平流有关外,还与高空动量下传的地点和时间密切相关,对于寒潮过程中的降水而言,低层的温度层结及其水汽输送特点,决定了不同地区的相态变化和降水的量级。通过关注环流相似寒潮过程中的爆发方式和动力过程,对于正确预报寒潮天气造成的不同地区的降温、大风、沙尘和降水具有很好的借鉴意义。展开更多
文摘The present article is focused on modelling of flow and heat transfer behaviour of Cu-water nanofluid in a confined slot jet impingement on hot moving plate.Different parameters such as various moving plate velocities,nanoparticles at various concentrations,variation in turbulent Reynolds number and jet nozzle to plate distance have been considered to study the flow field and convective heat transfer performance of the system.Results of distribution of local and average Nusselt number and skin friction coefficients at the plate surface are shown to elucidate the heat transfer and fluid flow process.Qualitative analysis of both stream function and isotherm contours are carried out to perceive the flow pattern and heat transfer mechanism due to moving plate.The results revealed that average Nusselt number significantly rises with plate velocity in addition with jet inlet Reynolds number.Correlations of the average Nusselt numbers are presented.
文摘The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field hut the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11890681,11832001,and 11988102)。
文摘We apply the heat jet approach to realize atomic simulations at finite temperature for a Frenkel–Kontorova chain with moving dislocation. This approach accurately and efficiently controls the system temperature by injecting thermal fluctuations into the system from its boundaries, without modifying the governing equations for the interior domain. This guarantees the dislocation propagating in the atomic chain without nonphysical damping or deformation. In contrast to the non-equilibrium Nosé–Hoover heat bath, the heat jet approach efficiently suppresses boundary reflections while the moving dislocation and interior waves pass across the boundary. The system automatically returns back to the equilibrium state after all non-thermal motions pass away. We further apply this approach to study the impact of periodic potential and temperature field on the velocity of moving dislocation.
基金co-supported by the National Natural Science Foundation of China (Nos. 11272150 and 11572156)
文摘The effects of synthetic jet control on unsteady dynamic stall over rotor airfoil are investigated numerically. A moving-embedded grid method and an Unsteady Reynolds Averaged Navier-Stokes（URANS） solver coupled with k-x Shear Stress Transport（SST） turbulence model are established for predicting the complex flowfields of oscillatory airfoil under jet control. Additionally, a velocity boundary condition modeled by sinusoidal function has been developed to fulfill the perturbation effect of periodic jet. The validity of present CFD method is evaluated by comparisons of the calculated results of baseline dynamic stall case for rotor airfoil and jet control case for VR-7 B airfoil with experimental data. Then, parametric analyses are conducted emphatically for an OA212 rotor airfoil to investigate the effects of jet control parameters（jet location, dimensionless frequency, momentum coefficient, jet angle, jet type and dual-jet） on dynamic stall characteristics of rotor airfoil. It is demonstrated by the calculated results that efficiency of jet control could be improved with specific momentum coefficient and jet angle when the jet is located near separation point of rotor airfoil. Furthermore, the dual-jet could improve control efficiency more obviously on dynamic stall of rotor airfoil with respect to the unique jet, and the influence laws of dual-jet＇s angles and momentum coefficients on control effects are similar to those of the unique jet. Finally,unsteady aerodynamic characteristics of rotor via synthetic jet which is located on the upper surface of rotor blade in forward flight are calculated, and as a result, the aerodynamic characteristics of rotor are improved compared with the baseline. The results indicate that synthetic jet has the capability in improving aerodynamic characteristics of rotor.
文摘对于环流特征相似的寒潮过程,其爆发的方式、产生的天气和影响的区域基本相似,但个别寒潮过程却存在较大的差异,造成预报上的误判。针对此类特例,基于常规气象观测资料,自动站观测资料和NCEP逐6 h 1°×1°再分析资料,应用天气学分析和诊断方法,对2014年4月24日（过程1）和5月1日（过程2）2次寒潮天气过程的环流、系统和爆发的动力、热力学机制等进行对比分析。结果表明：2次过程北半球中高纬500 h Pa环流形势均具有两脊一槽的环流特征。寒潮区域升温明显,前期平均温度分别比历史同期偏高1.0-7.3℃和0.1-10.7℃,500 h Pa冷槽和强锋区均在新疆北部堆积、爆发南侵;2次过程在爆发方式和成因上存在着较大的差异,过程1中促使寒潮爆发流场为横槽转竖,槽前疏散结构和正涡度平流使低槽切断出低涡并东南移,冷平流中心移至槽前,横槽转竖寒潮爆发。过程2为低槽东移,冷槽移过阿尔泰山和蒙古高原加深东移,冷空气入侵内蒙古,寒潮爆发。虽然2次过程均造成了全区范围的强降温,但由于上述影响方式和成因的不同,使得大风、沙尘暴和降水呈现出不同的影响特点。寒潮过程中大风和沙尘暴的分布除与冷平流有关外,还与高空动量下传的地点和时间密切相关,对于寒潮过程中的降水而言,低层的温度层结及其水汽输送特点,决定了不同地区的相态变化和降水的量级。通过关注环流相似寒潮过程中的爆发方式和动力过程,对于正确预报寒潮天气造成的不同地区的降温、大风、沙尘和降水具有很好的借鉴意义。
