磁场抑制自然对流的能量涨落分析

Bridgman方法常用于制作高性能单晶体，当晶体熔化时，由于密度差引起的自然对流会导致晶体质量的下降，通过外加磁场来抑制该自然对流，用Spectral elemenl方法对镓融体的三维非稳态自然对流进行了数值模拟，得到了Pr=0．019时，无外加磁场、横向磁场和纵向磁场时的脉动动能以及对流、粘性耗散和浮力作用导致脉动动能涨落随时间的变化，同时，对脉动动能涨落中起主要作用的对流导致的能量涨落的各分量做了进一步分析。对流是导致的脉动动能涨落的主要因素。而水平速度梯度是对流项的主要组成部分。

Analysis of the Kinetic Energy Fluctuations of Magnetic Field-suppressed Natural Convection

Bridgman method is often used for the fabrication of high-performance single crystals. During the melting of crystals the natural convection caused by a density difference will lead to a lowering of crystal quality. Through the use of an externally added magnetic field the natural convection was suppressed. By employing a spectral element method a numerical simulation was performed of the three-dimensional non-steady-state natural convection of a gallium melt. As a result, obtained was (when Pr = 0.019) a time-dependent variation of pulsating kinetic energy fluctuations caused by pulsating kinetic energy in the absence of an externally added magnetic field, transverse and longitudinal magnetic fields as well as by the convection, viscous dissipation and floating force action. Meanwhile, the various components representing energy fluctuations caused by the convection, which plays a major role in pulsation kinetic energy variation, undergo a further analysis. The convection is a key factor leading to fluctuations of pulsation kinetic energy, while the horizontal speed gradient constitutes a main constituent part of the convection item.