Implementation of material sensitivity analysis for determining unknown remanent magnetization of a ferromagnetic thin shell

This paper deals with the numerical implementation of the material sensitivity analysis, which is used to efficiently determine an optimal magnetization distribution on a ship hull. A material sensitivity formula for the forward problem formulated in terms of the equivalent magnetic charge method is analytically derived. Then, the components of the adjoint system including the magnetic pseudo-source are thoroughly investigated in order to obtain the first-order gradient information of an objective function with respect to the magnetic charge. The formula facilitates applying the deterministic approach to searching for an optimal charge distribution and also it yields stable and reliable solutions to magnetostatic inverse problems in three dimensions. Finally, the proposed method has been successfully applied to a scale model ship and the predicted results on the underwater field disturbance due to the remanent magnetization of the hull have been compared to real measurements.