Learning Forum

[Ashwin Subramanian Murugan]

Hello, Im trying to simulate the shock train in a supersonic inlet. I have attached a picture of my mesh.

Inlet - Pressure inlet - Total Pressure = 207Kpa, Static Pressure = 42Kpa (Mach 1.7) Total temp = 310K
Outlet - Pressure outlet - Static pressure = 1 Pa
Im supposed to get a nice series of shocks in the duct. However when I run the simulation, I find that initially the shock forms, with more iterations the location of the shock moves towards the inlet and disappears, Once it disappears the solution converges immediately.
How do I solve this problem?

[Federico Alzamora Previtali]

Hello, 

Which solver are you using? Pressure or Density-based? Which Solution methods and discretization schemes are you using?

can you show us a contour plot for the pressure? If you can, please include a snapshot of the intermediate solution (with the shocks) and the final solution.

[Ashwin Subramanian Murugan]

Hello, Thank you for your reply.
I am using the pressure based solver with coupled method and 2nd order discretization schemes. I also tried the density based solver, but it seems to take a lot more iterations to get to the same point.
After 150 iterations:

After 300 iterations:

500 iterations:
Converged solution:
Residuals drop sharply after the shock disappears and the inlet which was supersonic initially becomes subsonic.

Inlet was suppose to remain at mach 1.7 but after the shock disappears it becomes subsonic.

Kindly help, thanks.

[Ashwin Subramanian Murugan]

Hello, thank you for your reply.

I am using the pressure-based solver with coupled method and 2nd-order discretization schemes. I have also tried the density-based solver, but it seems to take many more iterations to get to the same point.
I have attached the contour plots and residuals.
Also, after the shock disappears, the inlet becomes subsonic, which is not what I set.
After fmg initialization:

after 150 iterations:

After 300 iterations:

After 500 :

After convergence:

Residuals and inlet Mach number:

Kindly help, Thanks

[Federico Alzamora Previtali]

What are your operating conditions?

Given your boundary conditions, are you sure that the nozzle exit is not choked?

[Ashwin Subramanian Murugan]

 

 

Operating pressure = 0 Pa
I’m referring a research paper that has experimental data. The outlet was connected to a vacuum pump so that’s why I set the outlet pressure to close to 0. How do I fix this? So I don't think it is choked.

 

 

[Ashwin Subramanian Murugan]

Hello everyone, Any suggestions would be really helpful, Thanks.