Hello! I’m trying to simulate a compressible supersonic flow along a convergent-divergent nozzle in a steady state, the expected Mach number is over 3, the pressure ratio around 70 and the inlet temperature around 2600K.
After reading some other post, I found that even if it is an steady-state, it’s recommended that I use the transient solver and a ramp inlet condition for the pressure, however, when I switch to it, the simulation run returns with an unespecified error. I tried both manually writing the table and importing a .csv table
I’m not sure if it is a bug regarding this type of condition or a mistake that I made while setting up the case. Here is the link to the proyect:
I think here the steady-state solution is adequate, you do not really need the transient solution to apply the ramp of the inlet boundary condition. Please refer to this tutorial for an example of this concept:
Other aspect is the wall: why are you using slip walls? Don’t you expect a boundary layer flow to happen in this situation? If so, what is the reason?
Finally, just as you extended the outlet, I would also extend the inlet to help stabilize the flow at the point of the nozzle.
Thank you for your reply, the problem is setting up the ramp condition, whenever I switch from a fixed value to a table value, the simulation returns with “an error has ocurred” and after checking the log, the simulation was not even able to start. I made a new run in the proyect with this settings, the error persists. The ramp recomendation was from this post
I was using the slip wall condition to get a preliminar result to get a little more stable simulation; my logic was that it shouldn’t crash as easly if I do not try to solve the boundary layer.
I see your table and it doesn’t make much sense to me. Your inlet pressure should start at ambient pressure such that no flow is created (same pressure as outlet), then ramp linearly up to your maximum value in a few hundred iterations. Refer to the tutorial and do the same!
Thanks again for the quick reply. I modified the geometry and the values to match both the outlet and the initial conditions, but the error still persist
The compressible solver available in the platform is pressure-based, so it’s best for velocities under Mach 1. For transonic/supersonic simulations, a density-based compressible solver would be best, however it’s currently not available for community users.
In short, mach 3 would be very unstable and very prone to divergence using solvers available for community users - feel free to provide feedback/suggestions here!
