On the development of OpenFOAM solvers for simulating MHD micropolar fluid flows with or without the effect of micromagnetorotation

Any micropolar fluid containing magnetic particles, such as blood and ferrofluids, under the influence of an applied magnetic field experiences a magnetic torque resulting from the misalignment between the magnetization of these particles and the magnetic field, called micromagnetorotation (MMR). Although critical in such fluids, MMR remains underexplored in blood flows, where erythrocyte magnetization is often neglected. To address this, two transient OpenFOAM solvers were developed: epotMicropolarFoam, for incompressible, laminar MHD micropolar flows, and epotMMRFoam, which extends the former by incorporating MMR. In epotMicropolarFoam, the PISO algorithm is used for pressure-velocity coupling, while the low-magnetic-Reynolds-number approximation is adopted for the MHD phenomena simulation. Micropolar effects are included by incorporating the microrotation–vorticity difference in the momentum equation, and solving the internal angular momentum equation. EpotMMRFoam also uses the PISO algorithm and the low-magnetic-Reynolds-number approximation with the MMR term included in the internal angular momentum equation. In this solver, a constitutive magnetization equation is also solved. Validation against the analytical MHD micropolar Poiseuille flow showed excellent accuracy (error <2%). Including MMR caused notable reductions in velocity (up to 40%) and microrotation (up to 99.9%), especially under strong magnetic fields and high hematocrit values. Without MMR, magnetic effects were minimal due to the blood’s low electrical conductivity. The simulations of 3D MHD artery and 2D MHD aneurysm flows supported these results. Especially in the aneurysm, MMR suppressed any recirculation cores, highlighting its stabilizing and shear-dampening effects. The solvers show strong promise for biomedical applications such as magnetic hyperthermia and targeted drug delivery.