A measurement of particle translation and rotation using magnetic particle tracking

Optical based diagnostic methods are ubiquitous in flow measurements. For example, the particle image velocimetry (PIV) is able to provide 2D or 3D information of an entire flow field with high resolution. However, the optical methods have two limits: they can hardly be used in an opaque environment, and most of them are not able to measure the spin rate of individual particles, which plays a key role in granular flow. To address these issues, a magnetic particle tracking (MPT) technique is developed. The principle is to reconstruct the position and orientation of a magnetic dipole based on its magnetic field distribution. A magnetic particle in motion has six degrees of freedom. Hence, the measurements at six or more positions in the field are sufficient for the reconstruction (assuming each position provides one field strength signal). The MPT does not need illumination, facilitating the measurement in the opaque environment, and more importantly, it is capable to measure the particle spin rate. In addition, the MPT has no harmful radiation and the measurement system is robust and easy to operate. Therefore, the MPT will have a wide application in the study of particulate flows.