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Seeking Guidance on Divergence Issues in Rocket Nozzle Flow Simulation for Heat Flux

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Old   December 12, 2023, 23:44
Unhappy Seeking Guidance on Divergence Issues in Rocket Nozzle Flow Simulation for Heat Flux
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Sean
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Hello SU2 community,

I hope this message finds you well. I am currently working on simulating the flow in a rocket nozzle with an isothermal wall condition to calculate heat flux along the wall. Despite my efforts, I have encountered divergence issues in my simulations.

Here are the details of my setup:

Physics:

Rocket nozzle flow simulation with an isothermal wall condition.

Numerics:
  • Attempted both SA (Spalart-Allmaras) and SST (Shear-Stress Transport) turbulence models.
  • Adjusted CFL (Courant-Friedrichs-Lewy) numbers to explore stability.
  • Mesh cell near the wall is orthogonal and approximately 8.e-06 away from the wall.
  • Despite these efforts, my simulation diverges over time.

I am reaching out to seek your valuable guidance on the following:

Recommendations for Stability:
  • Are there specific guidelines or recommendations for adjusting numerical parameters (CFL numbers, turbulence models) in rocket nozzle simulations to enhance stability?

Mesh Considerations:
  • Is there a particular aspect of meshing that I should focus on, especially near the wall, to ensure stability and accurate heat flux calculations?

Solver Settings:
  • Are there specific solver settings that are crucial for simulations involving rocket nozzles and heat flux calculations?

Validation Strategies:
  • Any insights on effective validation strategies for rocket nozzle simulations with isothermal wall conditions?

I appreciate any guidance or suggestions you can provide to help me overcome the divergence issues and obtain accurate heat flux results along the wall.

Thank you in advance for your assistance.

Best regards.
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Old   December 13, 2023, 03:48
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Shukai Wang
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hi, may you attach your cfg file so that we can take a look? that would be more convenient. thx.
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Old   December 13, 2023, 04:09
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Also the mesh, so we can reproduce your issue.
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Old   December 13, 2023, 04:24
Default Here are the links of the mentioned files
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https://drive.google.com/file/d/1pgD...ew?usp=sharing
https://drive.google.com/file/d/1scU...usp=drive_link
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Old   December 14, 2023, 00:18
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Quote:
Originally Posted by bigfootedrockmidget View Post
Also the mesh, so we can reproduce your issue.
Did you give it a try ?
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Old   December 14, 2023, 22:12
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I am stuck on the same problem, Can anyone suggest from the experience anything atleast ?
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Old   December 15, 2023, 04:11
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I had a brief look at it. It does not blow up when you switch off the MUSCL scheme, but the residuals at the wall stay very high for the energy equation.

If you switch from temperature to heat flux, this issue at the wall disappears. Not sure what the origin of this issue is, maybe it's related to the setup of the NICFD, I am not really familiar with it. Does this work for a regular ideal gas?
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diverged, heat flux, isothermal wall, nan error, nozzle flow

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