The efficiency and mechanism of an active control device ＂＇Spark Jet＂ and its application in shock-induced separation control are studied using large-eddy simulation in this paper. The base flow is the interaction ...The efficiency and mechanism of an active control device ＂＇Spark Jet＂ and its application in shock-induced separation control are studied using large-eddy simulation in this paper. The base flow is the interaction of an oblique shock-wave generated by 8° wedge and a spatially-developing Ma = 2.3 turbulent boundary layer. The Reynolds number based on the incoming flow property and the boundary layer displacement thickness at the impinging point without shock-wave is 20000. The detailed numerical approaches were presented. The inflow turbulence was generated using the digital filter method to avoid artificial temporal or streamwise periodicity. The , merical results including velocity profile, Reynolds stress profile, skin friction, and wall pressure were sys- tematically validated against the available wind tunnel particle image velocimetry （PIV） measure- ments of the same flow condition. Further study on the control of flow separation due to the strong shock-viscous interaction using an active control actuator ＂＇Spark Jet＇＂ was conducted. The single-pulsed characteristic of the device was obtained and compared with the experiment. Both instantaneous and time-averaged flow fields have shown that the jet flow issuing from the actuator cavity enhances the flow mixing inside the boundary layer, making the boundary layer more resis- tant to flow separation. Skin friction coefficient distribution shows that the separation bubble length is reduced by about 35% with control exerted.展开更多
反作用控制系统(reaction control system,RCS)在高超声速飞行器上取得了较为广泛的应用,已成为高超声速飞行器重要的控制手段之一.RCS工作过程中喷流与来流形成了复杂的干扰流场,使得对RCS的控制能力预测存在困难.根据RCS在不同高超声...反作用控制系统(reaction control system,RCS)在高超声速飞行器上取得了较为广泛的应用,已成为高超声速飞行器重要的控制手段之一.RCS工作过程中喷流与来流形成了复杂的干扰流场,使得对RCS的控制能力预测存在困难.根据RCS在不同高超声速飞行器上的布局位置及飞行器局部外形特点将RCS布局方式归纳为4类,包括小曲率表面喷流、大曲率表面喷流、头部喷流和翼面附近喷流.对用于模拟各布局方式流动特征的4种典型模型进行了概述,并对各典型模型喷流干扰问题的研究进展进行了总结.最后,对今后研究方向提出了一些建议.展开更多
Recent studies on high-multiplicity events in small collision systems(proton-proton and proton-lead)have drawn considerable research interest toward the possibility of the formation of partonic medium in such systems....Recent studies on high-multiplicity events in small collision systems(proton-proton and proton-lead)have drawn considerable research interest toward the possibility of the formation of partonic medium in such systems.One of the important consequences of the formation of dense partonic medium is the quenching of high-momentum final-state particles,resulting in several experimental observations such as suppression in nuclear modification factor RAA,modification of jet shape observableρ(r)and jet fragmentation(z^(ch))distributions,etc.In this work,we studyρ(r)and z^(ch)for inclusive charged-particle jets in proton-proton(pp)collisions at√s=13 TeV using the PYTHIA 8 Monash 2013 Monte Carlo simulation.We show that the color reconnection(CR)and multiparton interaction(MPI)mechanisms in PYTHIA 8 can lead to an increased rate of jet production.We also find that the mechanisms of MPI and CR and change in the gluonic contribution in high-multiplicity events result in significant modification ofρ(r)and z^(ch)compared to those in minimum bias events for 10<p_(T,jet)^(ch)<20 GeV/c.We notice a direct connection of<N_(MPI)>and gluonic contribution with the amount of modification inρ(r):the larger the number of MPIs and/or gluonic contribution,the larger the amount of modification ofρ(r).展开更多
喷流反作用控制系统(Reaction Control System,RCS)热喷高温燃气辐射效应对飞行器光学探测跟踪具有重要影响。基于谱带辐射模型,通过求解带化学反应源项的三维Navier-Stokes方程和辐射传输方程,对高超声速飞行器喷流反作用控制系统热喷...喷流反作用控制系统(Reaction Control System,RCS)热喷高温燃气辐射效应对飞行器光学探测跟踪具有重要影响。基于谱带辐射模型,通过求解带化学反应源项的三维Navier-Stokes方程和辐射传输方程,对高超声速飞行器喷流反作用控制系统热喷干扰流场及其红外辐射特性进行了数值模拟,分析了二次燃烧效应、不同飞行条件以及不同观测角度对流场红外辐射特性的影响。研究表明:典型状态喷流辐射计算与实验测量结果一致,流场与红外辐射数值方法具有较好的适应性;飞行器RCS工作所形成热喷干扰流场的红外辐射,主要由喷流燃气中的CO_(2)和H_(2)O组分贡献,其中CO_(2)对辐射的贡献更大,流场中二次燃烧效应对流场辐射强度有显著影响,在20 km高度下可使流场辐射强度提高一倍以上;随着马赫数/高度的增加,流场辐射强度均呈现先略有减小,后增大的趋势,随着高度增加,二次燃烧效应对流场辐射强度的影响明显减弱;由飞行器RCS工作引起的辐射增量十分显著,俯视观测以及3~5μm波段的目标辐射强度最大。文中的研究结果可为飞行器探测跟踪提供参考。展开更多
This paper presents the interactions between two cold atmospheric plasma jets. By changing the experimental conditions including the gas flow rate, the applied voltage, the power supply frequency and the inter-electro...This paper presents the interactions between two cold atmospheric plasma jets. By changing the experimental conditions including the gas flow rate, the applied voltage, the power supply frequency and the inter-electrode distance d, three different interaction modes, attraction, repulsion and combination, were observed. It is shown that the interaction modes of the two jets are principally affected by the electrodes, the gas flow rate, the plasma jets and the power supply frequency.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11302012,51420105008,51476004,11572025 and 51136003)the National Basic Research Program of China(No.2012CB720205)The computational time for the present study was provided by the UK Turbulence Consortium(EPSRC grant EP/L000261/1)
文摘The efficiency and mechanism of an active control device ＂＇Spark Jet＂ and its application in shock-induced separation control are studied using large-eddy simulation in this paper. The base flow is the interaction of an oblique shock-wave generated by 8° wedge and a spatially-developing Ma = 2.3 turbulent boundary layer. The Reynolds number based on the incoming flow property and the boundary layer displacement thickness at the impinging point without shock-wave is 20000. The detailed numerical approaches were presented. The inflow turbulence was generated using the digital filter method to avoid artificial temporal or streamwise periodicity. The , merical results including velocity profile, Reynolds stress profile, skin friction, and wall pressure were sys- tematically validated against the available wind tunnel particle image velocimetry （PIV） measure- ments of the same flow condition. Further study on the control of flow separation due to the strong shock-viscous interaction using an active control actuator ＂＇Spark Jet＇＂ was conducted. The single-pulsed characteristic of the device was obtained and compared with the experiment. Both instantaneous and time-averaged flow fields have shown that the jet flow issuing from the actuator cavity enhances the flow mixing inside the boundary layer, making the boundary layer more resis- tant to flow separation. Skin friction coefficient distribution shows that the separation bubble length is reduced by about 35% with control exerted.
文摘反作用控制系统(reaction control system,RCS)在高超声速飞行器上取得了较为广泛的应用,已成为高超声速飞行器重要的控制手段之一.RCS工作过程中喷流与来流形成了复杂的干扰流场,使得对RCS的控制能力预测存在困难.根据RCS在不同高超声速飞行器上的布局位置及飞行器局部外形特点将RCS布局方式归纳为4类,包括小曲率表面喷流、大曲率表面喷流、头部喷流和翼面附近喷流.对用于模拟各布局方式流动特征的4种典型模型进行了概述,并对各典型模型喷流干扰问题的研究进展进行了总结.最后,对今后研究方向提出了一些建议.
基金the Inspire Fellowship research grant(DST/INSPIRE Fellowship/2018/IF180285).
文摘Recent studies on high-multiplicity events in small collision systems(proton-proton and proton-lead)have drawn considerable research interest toward the possibility of the formation of partonic medium in such systems.One of the important consequences of the formation of dense partonic medium is the quenching of high-momentum final-state particles,resulting in several experimental observations such as suppression in nuclear modification factor RAA,modification of jet shape observableρ(r)and jet fragmentation(z^(ch))distributions,etc.In this work,we studyρ(r)and z^(ch)for inclusive charged-particle jets in proton-proton(pp)collisions at√s=13 TeV using the PYTHIA 8 Monash 2013 Monte Carlo simulation.We show that the color reconnection(CR)and multiparton interaction(MPI)mechanisms in PYTHIA 8 can lead to an increased rate of jet production.We also find that the mechanisms of MPI and CR and change in the gluonic contribution in high-multiplicity events result in significant modification ofρ(r)and z^(ch)compared to those in minimum bias events for 10<p_(T,jet)^(ch)<20 GeV/c.We notice a direct connection of<N_(MPI)>and gluonic contribution with the amount of modification inρ(r):the larger the number of MPIs and/or gluonic contribution,the larger the amount of modification ofρ(r).
文摘喷流反作用控制系统(Reaction Control System,RCS)热喷高温燃气辐射效应对飞行器光学探测跟踪具有重要影响。基于谱带辐射模型,通过求解带化学反应源项的三维Navier-Stokes方程和辐射传输方程,对高超声速飞行器喷流反作用控制系统热喷干扰流场及其红外辐射特性进行了数值模拟,分析了二次燃烧效应、不同飞行条件以及不同观测角度对流场红外辐射特性的影响。研究表明:典型状态喷流辐射计算与实验测量结果一致,流场与红外辐射数值方法具有较好的适应性;飞行器RCS工作所形成热喷干扰流场的红外辐射,主要由喷流燃气中的CO_(2)和H_(2)O组分贡献,其中CO_(2)对辐射的贡献更大,流场中二次燃烧效应对流场辐射强度有显著影响,在20 km高度下可使流场辐射强度提高一倍以上;随着马赫数/高度的增加,流场辐射强度均呈现先略有减小,后增大的趋势,随着高度增加,二次燃烧效应对流场辐射强度的影响明显减弱;由飞行器RCS工作引起的辐射增量十分显著,俯视观测以及3~5μm波段的目标辐射强度最大。文中的研究结果可为飞行器探测跟踪提供参考。
基金supported by National Natural Science Foundation of China (Nos.50537020,50528707)
文摘This paper presents the interactions between two cold atmospheric plasma jets. By changing the experimental conditions including the gas flow rate, the applied voltage, the power supply frequency and the inter-electrode distance d, three different interaction modes, attraction, repulsion and combination, were observed. It is shown that the interaction modes of the two jets are principally affected by the electrodes, the gas flow rate, the plasma jets and the power supply frequency.
