Number of iterations needed to reach the convergence criterion (in this case |(R_pol/R_eq)_i + 1−(R_pol/R_eq)_i| < 10⁻¹¹) for the fixed rotation rate approach (red hue curves) and adaptive method (blue tint curves) presented in Sect. 3.3 (the radial and angular resolutions chosen were N = 1000 and L = 101, respectively). For each approach, the degree of convergence as a function of iteration number is shown for three rotation rates. In the fixed-rotation approach, a transient phase in which the rotation speed gradually increases must be included at the beginning. In the case of the adaptive method, the three curves overlap.