1. A computer-implemented method, using a computer processor, comprising: simulating a fluid flow in an aircraft environment to determine at least one aerodynamic coefficient characterizing an aerodynamic behavior of at least one element of the aircraft; providing a digital solution of equations modelling the fluid flow in said aircraft environment, according to a model configured using physical parameters of the fluid flow, said digital solution being made iteratively to obtain a first series of values of the aerodynamic coefficient indexed by a number of iterations; defining a criterion for convergence of said aerodynamic coefficient using processing means; selecting a determined set of terms belonging to said first series of values of the aerodynamic coefficient, as a function of said convergence criterion, using the processing means; defining a monotonic function configured to make a relatively expanding transformation in said determined set relative to a complement of said set, using the processing means, the transformation being contracting outside said set; applying said monotonic function on said first series to transform into a second series of values of the aerodynamic coefficient, said second series defining a global change to said aerodynamic coefficient with a local expansion in a convergence zone corresponding to said determined set, using the processing means; determining said aerodynamic coefficient by plotting a variation curve representative of said second series of values of the aerodynamic coefficient as a function of the number of iterations, using the processing means; and displaying said variation curve including an intrinsic zoom of said convergence zone giving details of the convergence of said aerodynamic coefficient, on output means, wherein a plot of said variation curve includes variations indexed by the number of iterations.