First results of movable limiter experiments and its effects on the tokamak plasma confinement

Limiters play a number of roles in the tokamak operation. It serves primarily to protect the wall from the plasma when there are disruptions, runaway electrons, or other instabilities and also the limiters localize the plasma–surface interaction. In this research, we presented the first results of movable limiter experiments and its effects on the tokamak plasma confinement. For this purpose, we designed, constructed, and installed a movable localized poloidal limiter, and then measured the effects of limiter position on the time intervals of plasma parameters such as plasma density, temperature, and energy confinement time. The results of effects of the movable limiter experiments on plasma confinement.     

On nonlinear artificial viscosity,discrete maximum principle and hyperbolic conservation laws

A finite element method for Burgers’ equation is studied. The method is analyzed using techniques from stabilized finite element methods and convergence to entropy solutions is proven under certain hypotheses on the artificial viscosity. In particular we assume that a discrete maximum principle holds. We then construct a nonlinear artificial viscosity that satisfies the assumptions required for convergence and that can be tuned to minimize artificial viscosity away from local extrema. The theoretical results are exemplified on a numerical example. AMS subject classification (2000)  65M20, 65M12, 35L65, 76M10     

Reducing numerical diffusion in interfacial gravity wave simulations

We demonstrate how the background potential energy is an excellent measure of the effective numerical diffusion or antidiffusion of an advection scheme by applying several advection schemes to a standing interfacial gravity wave. All existing advection schemes do not maintain the background potential energy because they are either diffusive, antidiffusive, or oscillatory. By taking advantage of the compressive nature of some schemes, which causes a decrease in the background potential energy, and the diffusive nature of others, which causes an increase in the background potential energy, we develop two background potential energy preserving advection schemes that are well‐suited to study interfacial gravity waves at a density interface between two miscible fluids in closed domains such as lakes. The schemes employ total variation diminishing limiters and universal limiters in which the limiter is a function of both the upwind and local gradients as well as the background potential energy. The effectiveness of the schemes is validated by computing a sloshing interfacial gravity wave with a nonstaggered‐grid Boussinesq solver, in which QUICK is employed for momentum and the pressure correction method is used, which is second‐order accurate in time. For scalar advection, the present background potential energy preserving schemes are employed and compared to other TVD and non‐TVD schemes, and we demonstrate that the schemes can control the change in the background potential energy due to numerical effects. Copyright © 2005 John Wiley & Sons, Ltd.     

非结构网格上一类满足局部极值原理的三阶精度有限体积方法

对二维标量双曲型守恒律方程,发展了一类满足局部极值原理的非结构网格有限体积格式.其构造思想是,以单调数值通量为基础,通过应用基于最小二乘法的二次重构和极值限制器,使数值解满足局部极值原理.为保证数值解在光滑区域达到三阶精度,该格式可结合局部光滑探测器使用.本文从理论上分析了格式的稳定性条件,数值实验验证了格式的精度和对间断的分辨能力.     

感应屏蔽型高温超导故障电流限制器测试系统

根据感应屏蔽型高温超导故障电流限制器的基本原理 ,研制了一套限流器动态性能测试系统 ,用于实时检测在额定状态和故障状态下限流器的电流、电压。详细地阐述了该测试系统的基本原理 ,给出了系统的软、硬件组成及实验结果     

通量限制器对算法性能的影响

在非正交曹线坐标系下,本文给出了求解非线性双曲型Ｅｕｌｅｒ方程的ＬＵ－ＡＵＳＭＬＷ算法。为了改进该算法的性能,将高分辨率ＡＵＳＭＰＷ格式的空间精度由一阶精度扩展到三阶精度。分析了选择通量限制器对算法稳定性、收敛性和精度的影响,并构造了一种新的能量限制器。本文数值结果表明,通量限制器是决定ＬＵ－ＡＵＳＭＰＷ算法性能的关键因素,并且该算法采用本文构造的通量限制器,求解非线性双曲型Ｅｕｌｅｒ方程,具有较     

Compact third-order limiter functions for finite volume methods

We consider finite volume methods for the numerical solution of conservation laws. In order to achieve high-order accurate numerical approximation to non-linear smooth functions, we introduce a new class of limiter functions for the spatial reconstruction of hyperbolic equations. We therefore employ and generalize the idea of double-logarithmic reconstruction of Artebrant and Schroll [R. Artebrant, H.J. Schroll, Limiter-free third order logarithmic reconstruction, SIAM J. Sci. Comput. 28 (2006) 359-381].     

一种混合型桥式高温超导限流器的研究

提出一种改进的桥式高温超导限流器拓扑结构。将不同高温超导体制成的限流电阻与限流电感同时串人桥式限流回路。正常状态下，限流电感与限流电阻均为超导态，限流器呈现低阻抗．故障状态下，限流电感保持超导态。利用电感抑制故障电流的快速增加；同时，由于故障电流超过限流电阻的临界电流值。超导体迅速失超导致线路阻抗突然增大。可以限制故障电流稳态值．本文进行了限流原理的理论分析，并进行了系统仿真．结果表明，该拓扑结构同时利用了超导体超导态的电感和失超后的电阻来限制故障电流，限流效果好，响应和复位速度快，是对桥式限流结构和混合型限流原理的有意义的探索．     

A selection limiter of DSMC for near continuum flows

A selection limiter for the direct simulation monte carlo (DSMC) method is proposed to simulate near continuum flows. The selection limiter is calculated according to a continuum breakdown parameter and is used to limit the number of potential collision pairs. A Couette flow, a supersonic flow into a pitot probe and a nozzle plume flow are studied and compared with the standard DSMC to validate present method. It is found that its computational cost is about 35% of that of the standard DSMC method with satisfactory accuracy in the near continuum regime.     

求解双曲守恒律方程的高分辨率熵相容格式

为提高熵相容格式的精度,利用限制器机制构造高分辨率格式,将构造的通量限制器插入熵相容格式,得到一类高分辨率熵相容格式.构造Euler方程高分辨率熵相容格式时,对熵相容格式中的几个参数做简单调整,提高了接触间断处的分辨率.将所得格式的数值结果与熵相容格式的数值结果比较表明,构造的高分辨率熵相容格式具有稳健和基本无振荡等特性.