The effects of magnetic-field direction and magnitude on forced convection of aluminum oxide-water nanofluid over a circular cylinder

In this paper, the forced convection of Al2O3-water nanofluid over a circular cylinder inside a magnetic field is simulated and studied. The Navier-Stokes and energy equations are discretized using the finite element method. The nanoparticles and base fluid are aluminum oxide and water. An experimental model as a function of the temperature, nanoparticle diameter, and volume fraction of the nanofluid is utilized to calculate the nanofluid's viscosity and conductivity coefficient. In addition, some cases are compared with the analytical model of Brinkman-Maxwell that is a function of the volume fraction of the nanofluid. The ranges of the main parameters, including the Reynolds numbers, Hartman numbers, angles of magnetic field, and volume fractions of the nanofluid, are 40 <= Re <= 200, 0 <= Ha <= 100, 0 <= gamma <= 90 and 0 <= phi <= 0.06, respectively. The results for local and average Nusselt numbers, drag and lift coefficients, and streamlines are presented and discussed. The findings show that the model of the nanofluids is important, and the values of the Nusselt numbers in the experimental model are different than the Brinkman-Maxwell analytical one. The value of the Nusselt number is increased with increasing of the Reynolds number and the angle of the magnetic field. In addition, the change in the Nusselt number with the Hartmann number depends on the angle of the magnetic field. The variation of the Nusselt number with the volume fraction of the nanofluid is almost increasable; however, the rate of that is dependent on the Reynolds number, the Hartmann number, and the angle of the magnetic field.