Transient free convection from a horizontal cylinder placed in a micropolar fluid

The problem of transient free convection from an isothermal cylinder placed horizontally in a micropolar fluid is investigated. The full governing equations of momentum, angular momentum (microrotation) and energy have been solved to give the details of flow and thermal fields. The main controlling parameters are Ra, Pr and material parameters, A and B. The study considered a range of Rayleigh number, Ra up to 104, a range for dimensionless vortex viscosity, A from 0 to 5 and a range for dimensionless spin viscosity, B from 0.1 to 10. Both Prandtl number, Pr and dimensionless spin gradient viscosity, are kept constant at 0.7 and I respectively. Results are presented for the local and average Nusselt numbers along with some details of flow and thermal fields. The study showed that in comparison with Newtonian fluids the micropolar fluids display a reduction in heat transfer rate.