Euler1D AUSM1

1st version of the AUSM method for the Euler equation

Uses the original FVS method by Liou and Steffen, with a simpler pressure split, to solve the 1D Euler equations. A PDE/ODE split accounts for an added source term, that allows solutions for plain 1D (alpha = 0), cylindrical symmetric (alpha = 1) and spherical symmetric (alpha = 2) flows. Initial data and BCs are suitable for a Riemann problem.
When refining the grid, a new suitable time-step is computed by taking CFL = 0.9 and dt = CFL*dt/max(S1,S3), where Si = max(max(abs(Li))), and Li are the three associated eigenvalues L1 = u-a, L2 = u and L3 = u+a.
Ideal gas relations are assumed (p = rho*R*T), with R = 287 and gamma = 1.4 for air. If using the axisymmetric versions, suggest setting xL = 0, in order to center the flow. More information on the numerics are found on E. Toro's book and the original paper by Liou and Steffen.
This code is very good for benchmarking 2D and 3D commercial codes by means of comparing shock tube problem solutions. A 2nd version using a modified pressure split is available as Euler1D AUSM2.