Cebers A
Institute of Physics, University of Latvia, Salaspils-1, LV-2169, Latvia.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Jan;61(1):700-8. doi: 10.1103/physreve.61.700.
Equations describing the kinetics of the phase separation in ferrocolloids in a Hele-Shaw cell under the action of a rotating magnetic field are proposed. Numerical simulation on the basis of a pseudospectral technique demonstrates that upon the action of a rotating field on a magnetic colloid which undergoes the phase separation a periodical system of stripes parallel to the plane of a rotating magnetic field stripes is created. The period of a structure found numerically satisfactorily corresponds to the one calculated on the basis of the energy minimum. Thus, the undulation instability leading to the formation of chevron structures takes place if the tangential component of a rotating magnetic field is eliminated, whereas the normal component is increased at the same time. If during the development of the undulation deformations of a concentration pattern the magnetic Bond number is large enough the secondary instabilities may occur leading to the fingering of stripes to bring about merging and break-up of stripes. It is shown that an increase in the magnetic Bond number leads to the onset of the instability at the boundaries between the regions with homogeneous orientation of stripes as well as to formation of the characteristic hairpin patterns.
提出了描述在旋转磁场作用下，铁胶体在Hele-Shaw盒中相分离动力学的方程。基于伪谱技术的数值模拟表明，在旋转磁场作用于经历相分离的磁性胶体时，会产生与旋转磁场条纹平面平行的周期性条纹系统。通过数值方法找到的结构周期与基于能量最小值计算出的周期令人满意地相符。因此，如果消除旋转磁场的切向分量，同时增加法向分量，就会发生导致人字形结构形成的波动不稳定性。如果在浓度图案的波动变形发展过程中，磁邦德数足够大，可能会出现二次不稳定性，导致条纹出现指状现象，从而使条纹合并和破裂。结果表明，磁邦德数的增加会导致条纹均匀取向区域之间的边界处出现不稳定性，以及形成特征性的发夹图案。
