Dynamics and Morphological Evolution of Ferrofluid Droplet under the Influence of Magnetic Field

• Author / Creator

  Ahmed,Abrar

• Owing to the spectacular adaptability and unique but non-intuitive shape evolution ability, ferrofluid is leveraged as an alternative for many applications ranging from sealing in bearing to manufacturing and droplet based microfluidics. However, there are numerous unanswered questions and unexplored phenomena in case of ferrofluid droplet dynamics, which are attempted to be addressed in this study. In this thesis, several aspects of drop impact dynamics, maneuvering and an essence of the coalescence behavior of ferrofluid droplet under the influence of magnetic field has been analyzed both theoretically and experimentally. Firstly, we explained the transient variation in morphology of an impinging droplet before and after the impact, which was studied with the presence of magnetic field with various strengths and directions. Through extensive experimental investigation a new phenomenological evidence was observed, where ratio of drop shape parameters before the impact and after the impact with minimal impacting energy remain constant regardless of magnetic field strength and magnetic field direction. We also gave a careful attention on the effect of magnetic field on the generation of satellite droplet during the drop deposition process and its final destination and travel path. Then we identified critical vertically oriented magnetic field, which would govern whether the satellite droplet would merge with the already deposited droplet or not, however under radial magnetic field satellite droplet always retract back to the needle. We also proposed a theoretical model for drop impact dynamics for a magnetically actuated ferrofluid droplet on a solid substrate. We developed a generalized mathematical formulation where the maximum spreading ratio (maximum spreading diameter/initial diameter of the droplet) is a function of numerous nondimensional parameters dictating the inertia, viscous, capillary and magnetic effects which are represented in the form of Weber number, Reynolds number and magnetic Bond number. We also validated this theoretical statement with comprehensive experimental investigations. Finally, we gave an explanation on the ferrofluid droplet coalescence under the effect of magnetic field, which will give us a complete insight on the application of ferrofluid as a potential element for 3D printing.  

• Subjects / Keywords

  • Satellite droplet
  • Droplet
  • Ferrofluid
  • Maximum spreading

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3SB3XD7H

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.