In this paper, we reengineer the flow field computation module. This module generates a structured and an automatic mesh and in the next step it solves the potential equation of the flow field. The key concepts is to recall the use of the finite element method in solving Laplacian problem. We will show the feasibility of the full potential equation in the simulations of bi-dimensional steady compressible flows. Formally, we suggest an easiest version in order to generalize it in the future. This work is summarized by converting the old version which is writing in Fortran 77 to another programming language Fortran 90.