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Supersonic Ramp Simulation

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Old   September 10, 2022, 20:15
Exclamation Supersonic Ramp Simulation
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Gurjot Ahuja
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Hello All,

I am a beginner in Ansys CFX. I have to simulate a supersonic flow Ma=3.2, Air Ideal Gas, 850K for laminar conditions, frictionless walls to analyze shock waves and expansion fans.
As per the theory, I have to set 5 independent variables as inlet conditions. So, I can set Total Temperature, 3 x Velocities directly from the given conditions and I am deriving Total Pressure for Inlet from Isentropic Relations and Ideal Gas Law. Is my approach correct to find the total pressure with is coming around 48.5 bar?
For Outlet, I am setting supersonic flow conditions in CFX Pre

When I am using Total Pressure as 48.5bar, my simulation is not converging at all.

Please help to resolve these issues.

Kind Regards.
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Old   September 10, 2022, 22:47
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Glenn Horrocks
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Please read the section titled "Using Boundary Condition" (section 2.3 of the Solver Modelling guide) and "Monitoring and Obtaining Convergence" (section 16.10 of the Solver Modelling Guide).

Make sure the basics are OK before we go too far.
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Old   September 11, 2022, 13:46
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If you look at your options for supersonic inlets, you have

1 - Velocity and Total Pressure
2 - Velocity and Static Pressure
3 - Static and Total Pressure

There is no need to convert anything, nor use any relationships.

Have you tried say M= 1.5, then 2.0, 2.5, 3.0 ? What is the solution for those intermediate flows?

What did I miss?
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Old   September 11, 2022, 14:56
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Gurjot Ahuja
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Quote:
Originally Posted by ghorrocks View Post
Please read the section titled "Using Boundary Condition" (section 2.3 of the Solver Modelling guide) and "Monitoring and Obtaining Convergence" (section 16.10 of the Solver Modelling Guide).
Thanks for the reply. I will check the documentation.

Last edited by tum-student; September 11, 2022 at 15:10. Reason: Update
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Old   September 11, 2022, 15:01
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Quote:
Originally Posted by Opaque View Post
If you look at your options for supersonic inlets, you have

1 - Velocity and Total Pressure
2 - Velocity and Static Pressure
3 - Static and Total Pressure

There is no need to convert anything, nor use any relationships.
Thanks for the reply. The strange thing is that the simulation is running successfully with Static Pressure but crashing with Total Pressure.

Quote:
Originally Posted by Opaque View Post
Have you tried say M= 1.5, then 2.0, 2.5, 3.0 ? What is the solution for those intermediate flows?

What did I miss?
My requirement is to do laminar and turbulent simulation only for M 3.2, so I haven't tried other Mach numbers. First, I am trying to set up a laminar simulation.
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Old   September 11, 2022, 18:29
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Quote:
Originally Posted by tum-student View Post
My requirement is to do laminar and turbulent simulation only for M 3.2, so I haven't tried other Mach numbers. First, I am trying to set up a laminar simulation.
I guess like all of us, you crawled, stood up, walk, and ran in sequence. Doubt your parents forced you to run before being able to stand.

Regardless of requirements, you must always follow common sense and understand one step at a time.

Good luck with your simulations.
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