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Up to now, no a real liquid metal (LM) free surface flow have been successfully used in magnetic fusion devices as MHD instability and unavoidable rivulet flow. Recently, after we carried out a guidable free curve-surface flow on theoretically and experimentally, seeking for other way to get a full-cover free surface flow is also in implementing. The superficial layer MHD effect in free surface flow is experimentally observed. After compared and analyzed the characteristic parameters of the free surface flow, the new two parameters of surface cover ratio and rivulet flow index are introduced to characterize the flowing characteristic of the full-cover free surface flow under magnetic field. According to the analysis rule, for different liquid metal, there are the different unique conditions to meet full-cover free surface flow under magnetic field.

Liquid metal magnetohydrodynamic (MHD) flows through the electrical coupling rectangular ducts are investigated based on a fully developed modeling. Numerical simulations of four different coupling MHD duct flows are carried out to get the results of the MHD pressure drop and the velocity distribution. The first and second cases are that the coupling rectangular ducts are arranged along the direction of external magnetic field, the flow direction in the two ducts is the same in case 1 but it is opposite in case 2; in the third and fourth cases another coupling duct is extended along the perpendicular direction of the external magnetic field, the flow direction is identical in case 3 but it is opposite in case 4. Numerical results of the velocity and the induced electrical current distributions in the cross sections of the coupling ducts are given in those four different cases, it is indicated that the external magnetic field has a different effect on the flow pattern in those four cases. The MHD pressure drop in those four different cases are compared with the result of one normal rectangular duct flow, the MHD pressure drop of case 1 is reduced compare to the result of one normal duct MHD flows and result of case 4 is almost the same as one normal duct but the results of case 2 and 3 are larger than it, especially in case 2 it is several times larger than the result of one normal duct flow, in addition, the MHD pressure gradient decreases with the increase of the wall conductance ratio. These results are very important and should be considered in the future liquid blanket design.