本文对托卡马克的符号辅助计算特征值和线性求解程序(symbolic computation aided eigenvalue and linear code for Tokamaks,SCELT)进行了并行开发及功能拓展。具体为优化了非均匀网格加密的功能,提高了程序的收敛速度和收敛精度;增加...本文对托卡马克的符号辅助计算特征值和线性求解程序(symbolic computation aided eigenvalue and linear code for Tokamaks,SCELT)进行了并行开发及功能拓展。具体为优化了非均匀网格加密的功能,提高了程序的收敛速度和收敛精度;增加了程序对稀疏矩阵功能的支持,减少了程序对内存的消耗;使用并行思想和信息传递接口(message passing interface,MPI)技术对程序数值离散模块并行开发,通过多进程并行提高了程序数值离散的效率。同时,基于特征值问题计算的可扩展库(the scalable library for eigenvalue problem computations,SLEPc)特征值求解库为程序添加了大规模稀疏矩阵特征值并行求解功能,提高了程序研究问题的速度以及规模。通过计算内扭曲模(m=1,n=1)和电阻撕裂模(m=2,n=1)的线性增长率和模结构验证了并行及拓展后的程序的可靠性。此外,通过与初始版本的运行结果进行比较,展示了优化后的程序在运行速度、运行规模上的巨大优势,以及程序在研究复杂的磁流体动力学(magnetohydrodynamic,MHD)特征值问题的潜力。展开更多
An in-depth and comprehensive understanding of the complex nonlinear behaviors in atmospheric dielectric barrier discharge is significant for the stable operation and effective control of the plasma. In this paper, we...An in-depth and comprehensive understanding of the complex nonlinear behaviors in atmospheric dielectric barrier discharge is significant for the stable operation and effective control of the plasma. In this paper, we study the nonlinear behaviors in argon atmospheric dielectric barrier multi pulse discharges by a one-dimensional fluid model. Under certain conditions, the multi pulse discharge becomes very sensitive with the increase of frequency, and the multi pulse period-doubling bifurcation, inverse period-doubling bifurcation and chaos appear frequently. The discharge can reach a relatively steady state only when the discharges are symmetrical between positive and negative half cycle. In addition, the effects of the voltage on these nonlinear discharges are also studied. It is found that the amplitude of voltage has no effects on the number of discharge pulses in multi-pulse period-doubling bifurcation sequences; however, to a relatively stable periodic discharge, the discharge pulses are proportional to the amplitude of the applied voltage within a certain range.展开更多
The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the disch...The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period-n discharge becomes more and more unstable with the increase of n. The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied.It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation.展开更多
The linear behavior of the dominant unstable mode(m=2,n=1)and its high order harmonics(m=2n,n≥2)are numerically investigated in a reversed magnetic shear cylindrical plasma with two q=2 rational surfaces on the basis...The linear behavior of the dominant unstable mode(m=2,n=1)and its high order harmonics(m=2n,n≥2)are numerically investigated in a reversed magnetic shear cylindrical plasma with two q=2 rational surfaces on the basis of the non-reduced magnetohydrodynamics(MHD)equations.The results show that with low beta(beta is defined as the ratio of plasma pressure to magnetic field pressure),the dominant mode is a classical double tearing mode(DTM).However,when the beta is sufficiently large,the mode is driven mainly by plasma pressure.In such a case,both the linear growth rate and mode structures are strongly affected by pressure,while almost independent of the resistivity.This means that the dominant mode undergoes a transition from DTM to pressure-driven mode with the increase of pressure,which is consistent with the experimental result in ASDEX Upgrade.The simulations also show that the distance between two rational surfaces has an important influence on the pressure needed in mode transition.The larger the distance between two rational surfaces,the larger the pressure for driving the mode transition is.Motivated by the phenomena that the high-m modes may dominate over low-m modes at small inter-resonance distance,the high-m modes with different pressures and q profiles are studied too.展开更多
The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is fou...The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is found that the loss of fast ions produced by ICRH mainly appears in both ends of the resonance layer,while the loss of fast ions in the middle resonance layer is very small.The dominant fast loss comes from trapped ions,rather than from passing ions.Controlling the location of resonance layer at the plasma core may be more beneficial to the EAST tokamak ICRH.In addition,the loss distribution of fast ions is studied.The results show that the fast ions are mainly lost near the midplane in the poloidal direction,but almost uniformly in the toroidal direction.Moreover,we investigate the dependence of fast ion loss on the ICRH power.The simulation results show that the loss fraction of fast ions in both ends of the resonance region increases with the ion cyclotron range of frequencies(ICRF)power,but barely affects the loss of fast ions in the middle region.展开更多
文摘本文对托卡马克的符号辅助计算特征值和线性求解程序(symbolic computation aided eigenvalue and linear code for Tokamaks,SCELT)进行了并行开发及功能拓展。具体为优化了非均匀网格加密的功能,提高了程序的收敛速度和收敛精度;增加了程序对稀疏矩阵功能的支持,减少了程序对内存的消耗;使用并行思想和信息传递接口(message passing interface,MPI)技术对程序数值离散模块并行开发,通过多进程并行提高了程序数值离散的效率。同时,基于特征值问题计算的可扩展库(the scalable library for eigenvalue problem computations,SLEPc)特征值求解库为程序添加了大规模稀疏矩阵特征值并行求解功能,提高了程序研究问题的速度以及规模。通过计算内扭曲模(m=1,n=1)和电阻撕裂模(m=2,n=1)的线性增长率和模结构验证了并行及拓展后的程序的可靠性。此外,通过与初始版本的运行结果进行比较,展示了优化后的程序在运行速度、运行规模上的巨大优势,以及程序在研究复杂的磁流体动力学(magnetohydrodynamic,MHD)特征值问题的潜力。
基金supported by National Natural Science Foundation of China(No.11447244)the Science Foundation of Hengyang Normal University of China(No.14B41)+1 种基金the Construct Program of the Key Discipline in Hunan Provincethe Hunan Provincial Applied Basic Research Base of Optoelectronic Information Technology of China(No.GDXX010)
文摘An in-depth and comprehensive understanding of the complex nonlinear behaviors in atmospheric dielectric barrier discharge is significant for the stable operation and effective control of the plasma. In this paper, we study the nonlinear behaviors in argon atmospheric dielectric barrier multi pulse discharges by a one-dimensional fluid model. Under certain conditions, the multi pulse discharge becomes very sensitive with the increase of frequency, and the multi pulse period-doubling bifurcation, inverse period-doubling bifurcation and chaos appear frequently. The discharge can reach a relatively steady state only when the discharges are symmetrical between positive and negative half cycle. In addition, the effects of the voltage on these nonlinear discharges are also studied. It is found that the amplitude of voltage has no effects on the number of discharge pulses in multi-pulse period-doubling bifurcation sequences; however, to a relatively stable periodic discharge, the discharge pulses are proportional to the amplitude of the applied voltage within a certain range.
基金supported by the National Natural Science Foundation of China(Grant Nos.11447244 and 11405208)the Science Foundation of Hengyang Normal University,China(Grant No.14B41)the Hunan Provincial Applied Basic Research Base of Optoelectronic Information Technology,China(Grant No.GDXX010)
文摘The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period-n discharge becomes more and more unstable with the increase of n. The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied.It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation.
基金Project supported by the Research Foundation of Education Bureau of Hunan Province,China (Grant No.21B0648)the National Natural Science Foundation of China (Grant Nos.11805239,12075282,and 11775268)the Natural Science Foundation of Hunan Province,China (Grant No.2019JJ50011)。
文摘The linear behavior of the dominant unstable mode(m=2,n=1)and its high order harmonics(m=2n,n≥2)are numerically investigated in a reversed magnetic shear cylindrical plasma with two q=2 rational surfaces on the basis of the non-reduced magnetohydrodynamics(MHD)equations.The results show that with low beta(beta is defined as the ratio of plasma pressure to magnetic field pressure),the dominant mode is a classical double tearing mode(DTM).However,when the beta is sufficiently large,the mode is driven mainly by plasma pressure.In such a case,both the linear growth rate and mode structures are strongly affected by pressure,while almost independent of the resistivity.This means that the dominant mode undergoes a transition from DTM to pressure-driven mode with the increase of pressure,which is consistent with the experimental result in ASDEX Upgrade.The simulations also show that the distance between two rational surfaces has an important influence on the pressure needed in mode transition.The larger the distance between two rational surfaces,the larger the pressure for driving the mode transition is.Motivated by the phenomena that the high-m modes may dominate over low-m modes at small inter-resonance distance,the high-m modes with different pressures and q profiles are studied too.
基金supported by National Natural Science Foundation of China (No. 11805239)the Natural Science Foundation of Hunan Province (No. 2019JJ50011)
文摘The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is found that the loss of fast ions produced by ICRH mainly appears in both ends of the resonance layer,while the loss of fast ions in the middle resonance layer is very small.The dominant fast loss comes from trapped ions,rather than from passing ions.Controlling the location of resonance layer at the plasma core may be more beneficial to the EAST tokamak ICRH.In addition,the loss distribution of fast ions is studied.The results show that the fast ions are mainly lost near the midplane in the poloidal direction,but almost uniformly in the toroidal direction.Moreover,we investigate the dependence of fast ion loss on the ICRH power.The simulation results show that the loss fraction of fast ions in both ends of the resonance region increases with the ion cyclotron range of frequencies(ICRF)power,but barely affects the loss of fast ions in the middle region.
