Magnetic-field effect on turbulent thermal convection of a nematic liquid crystal

We report on turbulent thermal convection of a nematic liquid crystal heated from below in a cylindrical cell with an aspect ratio (diameter/height) equal to 0.500 for Rayleigh numbers 2×10 < ∼ Ra < ∼ 3 × 10. The Nusselt number Nu as a function of Ra did not differ significantly from that of an isotropic fluid. In a vertical magnetic field H we found Nu(H)/Nu(0) = 1 + a(Ra)H with a(Ra) = 0.24Ra Gauss. We present a model that explains the H dependence in terms of a change of the thermal conductivity in the thermal boundary layers due to a field-induced director alignment.