Inception of vortical coherent structures from spinning magnetic nanoparticles in rotating magnetic fields – New nanofluid microscale mixing tool

• Mixing phenomena from interaction between magnetic field and magnetic fluid.
• Formation of coherent structures generated by rotating magnetic nanoparticles.
• Formation of rotating structures in uniform rotating magnetic fields.
• Eddy feature extraction using wavelet analysis.

To improve understanding of the mixing phenomena resulting from the interaction between uniform magnetic fields and magnetic nanofluids, this work presents an optical investigation of the coherent structures generated by rotating magnetic nanoparticles in dilute nanofluid suspension submitted to uniform rotating magnetic fields. A microscopic visualization technique was implemented inside the bore of an electromagnet to allow image and video capture of the variation in nanofluid behavior under time-varying magnetic fields and different operating parameters. The effects of magnetic core volume fraction, magnetic nanoparticle diameter, rotating magnetic field intensity and frequency as well as magnetic field type on coherent structure generation were explored. The observational results were subsequently correlated and analyzed making use of an automatic structure detection protocol at different scales based on multi-resolution orthogonal 2-Dimensional discrete wavelet transforms. All the parameters considered were found to substantially affect detectable structure inception in the nanofluid in different ways, with trends and thresholds emerging for different types of organisations at different scales. This information now opens the door for adequate tuning of rotating magnetic nanoparticle based mixing technologies at the micro-scale.

Newfangled visual and quantitative microscopic assessment of the effects of magnetic nanofluids and magnetic field parameters on resulting structure generation for micro-mixing applications.Figure optionsDownload as PowerPoint slide