This paper examines numerically the thermal and flow field characteristics of the laminar steady mixed
convection flow in a square lid-driven enclosure filled with water-based micropolar nanofluids by using
the finite volume method. While a uniform heat source is located on a part of the bottom of the enclosure,
both the right and left sidewalls are considered adiabatic together with the remaining parts of the
bottom wall. The upper wall is maintained at a relatively low temperature. Both the upper and left sidewalls
move at a uniform lid-driven velocity and four different cases of the moving lid ordinations are
considered. The fluid inside the enclosure is a water based micropolar nanofluid containing different types
of solid spherical nanoparticles: Cu, Ag, Al2O3, and TiO2. Based on the numerical results, the effects of
the dominant parameters such as Richardson number, nanofluid type, length and location of the heat
source, solid volume fractions, moving lid orientations and dimensionless viscosity are examined. Comparisons
with previously numerical works are performed and good agreements between the results are
observed. It is found that the average Nusselt number along the heat source decreases as the heat source
length increases while it increases when the solid volume fraction increases. Also, the results of the present
study indicate that both the local and the average Nusselt numbers along the heat source have the highest
value for the fourth case (C4). Moreover, it is observed that both the Richardson number and moving lid
ordinations have a significant effect on the flow and thermal fields in the enclosure.