A MPI Based Parallel Calculation Investigation On Two Dimensional Finite Element Modelling Of AEM

AEM(Airborne Electromagnetic Method)is one of the most commonly used branch of airborne geophysical method, which is widely used in geological survey, recourse exploration, environment monitoring and other related fields. Based on a thoroughly investigation in the features of all aspects of IMPULSE -one of the most popular frequency domain airborne electromagnetic systems, the importance of 2D modelling and inversion of AEM data was revealed. The 2D forward problem of AEM is actually to calculate the response of 2D geoelectrical model to a 3D source, which is also named 2.5D problem. During the practical procedure of calculating, the 2.5D Problem could be reduced to 2D problem through taking a Fourier transform along the strike direction because of its symmetry character on the strike.By using a free space as the distribution of background conductivity, the primary and secondary fields could be calculated separately, one by analytical solution and the other by FEM (Finite Element Method). Galerkin weighted residual method and isoparametric element with quadratic basis were both employed in calculating the secondary field .The system matrix for coupled equations is solved using the frontal solution, which is similar to Gaussian elimination except that the system matrix is never actually assembled and essentially reduce the computation cost. A serial code was developed by Fortran after finishing the formulating. The accuracy and efficiency of the code was tested by an simple layered model by comparing to the analytical solution which turned out to be that the 2D modelling algorithm is considerable reliable. Subsequently, the response of 8 different set of model and configurations were calculated by the code and analyzed for features.As the complexity of multi-dimensional frequency AEM modelling and inversion, parallelized attempt was made on the forward code for inversion consideration in the future. MPI(Message Passing Interface)is one of the most important standard in parallel programming, which leads to a domain decomposition algorithm and a SPMD(Single Program Multi data) idea. A small Cluster was built on which the parallel code was tested and turn out to increase the modelling process dramatically.