MHD-turbulence generation by cylinders in insulated ducts with different cross sections

Mercury experiments were performed to investigate the magnetohydrodynamic- (MHD)-turbulence generation by cylinders in ducts having two different cross sections: (i) a rectangular duct with two walls parallel to the orientation of the magnetic field B (side walls) and two sides perpendicular to B (Hartmann walls), and (ii) a trapezoid duct with one inclined Hartmann wall. The experiments covered the following ranges: the Reynolds number (Re)=2×103–104, the Hartmann number (Ha)=230–890, and the interaction parameter (N)=4–200. Distributions of the mean velocity and turbulence level downstream the cylinders were determined with two arrays of 20 electrodes. It is demonstrated that the turbulence is not damped in the rectangular duct compared with that in the trapezoid duct. In the latter one the damping is stronger in general in that part with the shorter side wall except for small distances. This might indicate that for small distances between turbulence promoters a heat transfer improvement might be also reached in this type of ducts.