Hey guys. Thank you for your replies.n1) Yeah I'm not happy with the cylindrical pipe's mesh at all, but I've been having difficulty generating a good one. The cells on the outer surface look very skewed to me, but if my mesh metrics are within the required ranges as specified by the tutorials, then what exactly defines my mesh as good enough or bad enough? What guidelines do you recommend I follow in order to generate a good enough mesh for this simulation? Is the rectangular shock tube's mesh bad too or is it just the pipe? n2) My boundary conditions are: ninlet is set as pressure-inlet --> Gauge total pressure is set to 101325 Pa, and supersonic/initial gauge pressure is set to 0 (i'm going to set this to 5731 Pa gauge because that is the pressure when the flow reaches M=1, is that what this parameter is defined as?) nleft and right planes are both set as pressure-outlet --> gauge pressure is set to 0 as that is the gauge pressure in my shock tube at those two locationsn3) My maximum Mach number at the pipe exit according to the generated contours at around 94,700 iterations of the transient sim is around 1.08, so there should be shocks in my flow. i miscalculated that earlier. should i switch to a density-based solver in this case? if so, implicit or explicit?n4) I'm using air as a compressible ideal gas, with density 1.225 kg/m3 at standard conditions.n5) I'm re-running the simulation now to capture contours at different stages as advised. I'll have them uploaded by tomorrow, as well as the variation in time steps. When do I know when to stop increasing the Courant number? At 0.5, the time step remains constant at 1e-8, and at 0.55, it also remains constant at 1e-5. But when I set it at 0.6, the time step starts to increase. Is this a sign that I should leave it at 0.55?n