Natural convection of an electrically conducting fluid under the different directions of
magnetic field in a horizontal cylindrical annulus is numerically studied using lattice Boltzmann
method (LBM). The inner and outer cylinders are maintained at uniform temperatures. Detailed
numerical results of heat transfer rate, temperature and velocity fields have been presented for salt
water with Pr=13.2, Ra=105 to 106 and Ha=0 to 100 for three directions of magnetic field. The
computational results reveal that in horizontal cylindrical annulus the flow and heat transfer are
suppressed more effectively by direction and intensity of magnetic field. It is also found that the
flow oscillations can be suppressed effectively by imposing an external horizontal magnetic field.
The average Nusselt number increases with rise in radius ratio but decreases with the Hartmann
number. Furthermore, it can be observed that there is a good agreement between the present result
and those predicted by available benchmark solutions under the limiting conditions.