Reconstructing a continuous magnetization field based on local vorticity cells, CFD and Langevin dynamics: A new numerical scheme

• Published in: Journal of magnetism and magnetic materials 2020-11, Vol.514, p.167135, Article 167135
• Main Authors: de Carvalho, D.D., Gontijo, R.G.
• Format: Article
• Language: English
• Subjects: Angular velocity; Channel flow; Demagnetization; Dipole moments; Ferrofluid flow; Ferrofluids; Ferrohydrodynamics; Langevin dynamics; Magnetic induction; Magnetic relaxation; Magnetization; Magnetization dynamics; Non-equilibrium magnetization; Vorticity
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2020.167135

•New way to avail the microstructure impact on non-equilibrium magnetization response.•Identification of a magnetic entrance length in ferrofluid channel flows.•Discussions on physical limits in which hydrodynamic-magnetic coupling is observed.•Identification of 3D effects in non-equilibrium regimes due to dipolar interactions. This work aims to reconstruct a continuous magnetization profile of a ferrofluid channel flow by using a discrete Langevin dynamics approach for the fluid’s micro structure. The continuous magnetization field is obtained through the coupled solution of 2D Ferrohydrodynamics equations in a CFD approach using a numerical code developed by the authors. The discrete Langevin Dynamics simulations consider a collection of magnetically interacting particles subjected to long-range field-dipole and dipole-dipole magnetic interactions. The particles are also subjected to hydrodynamic drag and to Brownian fluctuations for the translational and rotational motion. It is assumed that the dipole moments of the magnetic particles are fixed to their mechanical body, meaning they rotate along the particle’s angular velocity with no delay or advance. We identify an interesting demagnetization effect in the near wall region for moderate Brownian timescales associated with the competition between magnetic relaxation and flow’s vorticity.