Sound Wave Propagation in Two-Phase Flow of Magnetic Fluid

磁流体研究的进展引起了人们对磁流体技术应用的极大兴趣，并导致了许多有用装置的生产。然而，材料的物理性质尚未完全揭示。磁场作用下磁流体中的波传播问题是研究磁流体中高速流动特性的重要问题之一，已有文献对此进行了一些研究。然而，人们对两相磁流体知之甚少，而对两相磁流体的研究对磁流体实际工程应用的发展至关重要。对两相磁流体中声波的相速度进行了测量，发现声波的相速度随外加磁场强度的增大而增大。通过消除孔隙分数的影响，归一化的速度也随着场强的增加而增加，这不是由于流体中的分散关系。相速度的增加不能用均相两相流的计算来定量解释。这些结果与我们以前对两相磁流体中激波的研究是一致的。

The progress of magnetic fluid research has attracted considerable interest in the technological applications of magnetic fluids and led to the production of many useful devices. However, the physical properties of the materials have not yet been fully revealed. Wave propagation through magnetic fluid under a magnetic field is one of the important problems in studying the properties of high speed flow in magnetic fluids, and some studies on it have been described in the literatures. However, there exists little knowledge about two-phase magnetic fluids, whose investigations are very important for the development of practical engineering applications of magnetic fluids.We have measured phase velocity of sound waves in two-phase magnetic fluids, and found it increses with applied magnetic field strength. The velocity normalized by cancelling the effect of void fractions also increases with field strength, which does not result from a dispersion relationship in the fluids. The increase in phase velocity cannot explained quantitatively by calculation of homogenius two-phase flow. These results are compatible with our previous investigations on shock waves in two-phase magnetic fluids.