Numerical simulation of a liquid-metal flow in a poorly conducting pipe subjected to a strong fringing magnetic field

Using high resolution numerical simulations, we study the flow of a liquid metal in a pipe subjected to an intense decreasing magnetic field (fringing magnetic field). The chosen flow parameters are such that our study is directly relevant for the design of fusion breeder blankets. Our objectives are to provide a detailed description of the numerical method and of the results for benchmarking purposes but also to assess the efficiency of the so-called core flow approximation that models liquid-metal flows under the influence of intense magnetic fields. Our results are in excellent agreement with available experimental measurements. As far as the pressure drop is concerned, they also match perfectly the predictions of the core flow approximation. On the other hand, the velocity profiles obtained in our numerical simulations show a significant departure from this approximation beyond the inflection point of the magnetic field's profile. By plotting the momentum budget of the MHD equations, we provide evidence that this discrepancy can be attributed to the role of inertia that is neglected in the core flow approximation. We also consider a case with vanishing outlet magnetic field and we briefly illustrate the transition to turbulence arising in the outlet region of the pipe. (C) 2011 American Institute of Physics. [doi:10.1063/1.3570686]