Solis Kyle J, Martin James E
Sandia National Laboratories, Albuquerque, New Mexico, USA.
Soft Matter. 2014 Sep 7;10(33):6139-46. doi: 10.1039/c4sm00678j. Epub 2014 Jun 10.
We have recently reported on the discovery that an infinite class of triaxial magnetic fields is capable of producing rotational flows in magnetic particle suspensions. These triaxial fields are created by applying a dc field orthogonally to a rational biaxial field, comprised of orthogonal components whose frequencies form a rational ratio. The vorticity axis can be parallel to any of the three field components and can be predicted by a careful consideration of the symmetry of the dynamic field. In this paper we not only test the field-symmetry predictions, but also quantify fluid vorticity as a function of the field parameters (strength, frequency ratio, phase angle and relative dc field strength) and particle shape. These measurements validate the symmetry predictions and demonstrate that rational fields are as effective as vortex fields for producing strong fluid mixing, yet have the advantage that small changes in the frequency of one of the field components can change the vorticity axis. This approach extends the possibilities for noncontact control of fluid flows and should be useful in areas such as microfluidics, and the manipulation and mixing of microdroplets.
我们最近报道了一项发现，即一类无穷的三轴磁场能够在磁性粒子悬浮液中产生旋转流。这些三轴磁场是通过将直流磁场正交地施加到一个有理双轴磁场上而产生的，该双轴磁场由频率形成有理比的正交分量组成。涡度轴可以与三个场分量中的任何一个平行，并且可以通过仔细考虑动态场的对称性来预测。在本文中，我们不仅测试了场对称性预测，还将流体涡度量化为场参数（强度、频率比、相位角和相对直流场强度）以及粒子形状的函数。这些测量验证了对称性预测，并表明有理场在产生强流体混合方面与涡旋场一样有效，但具有这样的优势，即场分量之一的频率的小变化可以改变涡度轴。这种方法扩展了流体流动非接触控制的可能性，并且在微流体以及微滴的操纵和混合等领域应该会很有用。
