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Abstract: The reconstruction of the equilibrium of a plasma in a Tokamak is a free boundary problem described by the Grad–Shafranov equation in axisymmetric configuration. The right-hand side of this equation is a nonlinear source, which represents the toroidal component of the plasma current density. This paper deals with the identification of this nonlinearity source from experimental measurements in real time. The proposed method is based on a fixed point algorithm, a finite element resolution, a reduced basis method and a least-square optimization formulation. This is implemented in a software called Equinox with which several numerical experiments are conducted to explore the identification problem. It is shown that the identification of the profile of the averaged current density and of the safety factor as a function of the poloidal flux is very robust. [Copyright &y& Elsevier]

In the present work, fluid–structure interaction problems are analysed by means of optimised boundary element–finite element coupling procedures. The boundary element method is here employed to numerically model acoustic fluids and the finite element method is applied to discretise dynamic bodies (nonlinear effects included). Boundary element—finite element coupling is accomplished by an iterative algorithm: each boundary element or finite element sub-domain is analysed independently (as an uncoupled model) and a successive renewal of the variables at the common interfaces is performed, until convergence is achieved. The evaluation of an optimised relaxation parameter is introduced taking into account the minimisation of a square error functional. The algorithm that arises is more efficient and stable, representing an advancement of the iterative procedure. At the end of the paper, numerical examples are presented, illustrating the potentialities of the proposed methodology. [Copyright &y& Elsevier]