Mixed convective two phase flow of an electrically conducting micropolar nanofluid in a double lid-driven square cavity

We study the non-stationary, incompressible, laminar mixed-convection flow in a double lid–driven square enclosure filled with an electrically conducting micropolar nanofluid under the influence of an external magnetic field. The aim is to enhance understanding of heat and mass transport phenomena in nanofluids by examining the impact of key flow parameters — including the Grashof, Hartmann, Reynolds, and Prandtl numbers, as well as the micropolar material parameter, lid-motion parameter, Brownian motion, buoyancy ratio, and thermophoresis — on heat and mass transfer characteristics, expressed through local and average Nusselt and Sherwood numbers, streamlines, isotherms, microrotation, and concentration contours. The nanofluid is modeled as a two-phase mixture following a modified form of Buongiorno’s framework, which incorporates nanoparticle redistribution via an advection–diffusion concentration equation coupled with the Navier—Stokes equations. The governing system is solved numerically using a meshless point collocation method (MPCM), where spatial derivatives are computed through the Discretization-Corrected Particle Strength Exchange (DC PSE) technique, and transient terms are approximated using the Runge–Kutta–Fehlberg (RKF) scheme. This work is the first to couple Buongiorno’s two-phase nanofluid model with micropolar effects and magnetohydrodynamic (MHD) forces in a double lid–driven cavity. The results demonstrate that buoyancy enhancement (higher Gr) strengthens convection, whereas magnetic damping (higher Ha) suppresses it by flattening streamlines and thickening thermal layers. Tilting the magnetic field toward the vertical direction restores circulation and enhances heat transfer. Increasing the micropolar coupling parameter (K) augments microrotation and improves both heat and mass transport, partially counteracting magnetic damping. The lid-motion parameter ( λ ) governs flow symmetry: co-directional motion enhances, while counter-motion weakens convection, whereas higher nanoparticle concentration ( ϕ ) further boosts thermal performance due to increased effective conductivity. • Heat and mass transport is studied in a double lid-driven cavity with magnetohydrodynamic effects. • A micropolar extension of Buongiorno’s two-phase nanofluid model is numerically investigated. • A meshless point collocation method using the Discretization Correction Particle Strength Exchange method ensures simulation accuracy. • Microrotation effects can help explain gaps between numerical and experimental data. • Magnetic field orientation and material properties strongly affect transport rates.