托卡马克理想磁流体不稳定性的统一描述 (I)

在与平衡磁面相联系的坐标系下，用剪切阿尔芬波近似给出了统一描述托卡马克等离子体理想磁流体线性运动的本征模方程。利用此方程，可以进一步给出大尺度扰动（扭曲模、低模数气球模、阿尔芬模）和小尺度扰动（高模数气球模、Mercier模）的本征模方程。本文详细讨论了小尺度扰动的本征模方程。     

温度敏感型磁流体热磁对流特性研究

建立了描述外磁场作用下温度敏感型磁流体热磁对流特性的数学模型,数值模拟了回路中热磁对流的流动与传热特性.搭建了磁流体热磁对流回路装置,采用粒子示踪测速技术(PIV)测量了磁流体的流速,用热电偶测量了磁流体的温度分布.通过实验值和数值模拟结果,分析了不同磁场大小、不同热负荷,以及不同冷却温度下回路的运行特性.     

Co-Fe_3O_4磁流体稳定性的研究

研究了沉淀法制备Ｃｏ－Ｆｅ３Ｏ４磁流体过程中，工艺条件变化对Ｃｏ－Ｆｅ３Ｏ４磁流体稳定性的影响，从理论上对影响稳定性的因素进行了分析和解释，为研制高质量的磁流体提供了依据。     

霍耳效应与磁流体发电

 1879年,霍耳(E.H.Hall)发现,将一导电板放在垂直于板面的磁场中(见图1),当有电流通过时,在导电板的A和A′两侧会产生一个电势差UAA',这种现象称为霍耳效应。实验表明,霍耳电压UAA'与电流强度I和磁感应强度B成正比,而与导电板的厚度d成反比,即UAA'=KIdB式中比例系数K称为霍耳系数。霍耳效应是因外加磁场使漂移运动的电子或别的载流子发生横向偏转而形成的,运动电荷在磁场中所受的力称为洛伦兹力。磁流体发电是利用热离子气体(或液态金属)等导电流体与磁场相互作用,把热能直接转换成为电能的发电方式,它所依据的就是等离子体的霍耳效应。     

EXISTENCE AND STABILITY OF VISCOUS SHOCK PROFILES FOR 2-D ISENTROPIC MHD WITH INFINITE ELECTRICAL RESISTIVITY

For the two-dimensional Navier-Stokes equations of isentropic magnetohydrodynamics(MHD)withγ-law gas equation of state,γ≥1,and infinite electrical resistivity,we carry out a global analysis categorizing all possible viscous shock profiles.Precisely,we show that the phase portrait of the traveling-wave ODE generically consists of either two rest points connected by a viscous Lax profile,or else four rest points,two saddles and two nodes.In the latter configuration,which rest points are connected by profiles depends on the ratio of viscosities,and can involve Lax,overcompressive,or undercompressive shock profiles.Considered as three-dimensional solutions,undercompressive shocks are Lax-type(Alfven)waves.For the monatomic and diatomic casesγ=5/3 andγ=7/5,with standard viscosity ratio for a nonmagnetic gas,we find numerically that the the nodes are connected by a family of overcompressive profiles bounded by Lax profiles connecting saddles to nodes,with no undercompressive shocks occurring.We carry out a systematic numerical Evans function analysis indicating that all of these two-dimensional shock profiles are linearly and nonlinearly stable,both with respect to two-and three-dimensional perturbations.For the same gas constants,but different viscosity ratios,we investigate also cases for which undercompressive shocks appear;these are seen numerically to be stable as well,both with respect to two-dimensional and(in the neutral sense of convergence to nearby Riemann solutions)three-dimensional perturbations.     

ON THE SELF-SIMILAR SOLUTIONS OF THE MAGNETO-HYDRO-DYNAMIC EQUATIONS

In this paper, we show that, for the three dimensional incompressible magnetohydro-dynamic equations, there exists only trivial backward self-similar solution in L^p（R^3） for p ≥ 3, under some smallness assumption on either the kinetic energy of the self-similar solution related to the velocity field, or the magnetic field. Second, we construct a class of global unique forward self-similar solutions to the three-dimensional MHD equations with small initial data in some sense, being homogeneous of degree -1 and belonging to some Besov space, or the Lorentz space or pseudo-measure space, as motivated by the work in [5].     

Flow Reversal of Fully-Developed Mixed MHD Convection in Vertical Channels

The present analysis is concerned with flow reversal phenomena of the fully-developed laminar combined free and forced MHD convection in a vertical parallel-plate channel. The effect of viscous dissipation is taken into account. Flow reversal adjacent to the cold （or hot） wall is found to exist within the channel as Gr/Re is above （or below） a threshold value. Parameter zones for the occurrence of reversed flow are presented.     

磁流体中Helmholtz和Kelvin力的界定

磁流体磁彻体力的两种简化形式Helmholtz力和Kelvin力具有一定的适用范围.在推导磁流体中的磁彻体力表达式基础上,分析Helmholtz力和Kelvin力在磁流体中的起源,得出两种形式的成立条件.计算结果表明:当磁流体磁导率与外磁场强度无关时,磁流体磁彻体力可由Helmholtz力表示;当磁流体中磁性颗粒的平均磁矩与磁流体比体积无关时,Kelvin力为磁彻体力的简化形式;在磁流体磁化系数与其密度成正比情况下,Helmholtz力可转换为Kelvin力. 关键词： 磁流体 磁彻体力 Helmholtz力 Kelvin力     

MHD Flow Towards a Permeable Surface with Prescribed Wall Heat Flux

The steady magnetohydrodynamic （MHD） mixed convection flow towards a vertical permeable surface with prescribed heat flux is investigated. The governing partial differential equations are transformed into a system of ordinary differential equations, which is then solved numerically by a finite-difference method. The features of the flow and heat transfer characteristics for different values of the governing parameters are analysed and discussed. Both assisting and opposing flows are considered. It is found that dual solutions exist for the assisting flow, besides the solutions usually reported in the literature for the opposing flow.