Solution for a reflective cylinder initially immersed in a constant velocity flow of Mach 3, velocity 0.8, adiabatic index Γ = 1.4, and density 1.4. The main channel has length 10 and width 5, composed of 100 × 200 cells. The annulus has inner radius 0.5 and outer radius 1.25, with 168 cells in the angular dimension, and 32 cells in the radial direction, where an exponential stretching function has been applied in the radial direction to restrict the radial size of cells nearer the inner boundary. For clarity, we only show every other grid line. In the top half of the plot, contours of ρ at time t = 10 are shown. The scheme used was GFORCE¹, with the van Leer slope-limiter, at a CFL of 0.95. There are 30 contours, equally spaced between 0 and 10.