SimScale CAE Forum

Temperature field started diverging even when mesh is refined

Hi,

I have run multiple simulation and have got some results howeverm the last simulation that was run had a temperature divergence. I already refined my mesh by a lot and i am not sure how to fix this. It failed on Simulation Runs named "236.768m/s Mesh Refined”. Is there any way of fixing this.

Here is the Project File: https://www.simscale.com/workbench/?pid=7974882372988642661&mi=run%3A44%2Csimulation%3A24&mt=SIMULATION_RUN

Regards,

Syed

Hey there, what are the inlet conditions you wish to simulate (velocity and temperature)?

Best regards,
Fillia

The inlet velocity is 236.768m/s and the temperature is 218K

Regards,
Syed

Then maybe you should change the unit of temperature for a start (it is set in ° C right now)

Let me know how this goes :slight_smile:

Oh i did not see the units, thank you, i will try and run the simulation.

Regards,

Syed

1 Like

I have run the simulation and it still gave me a temperature divergence. I have check all the units and they are all correct now. But temperature divergence still remains.

Regards,
Syed

Could you tell me a bit more about the value of the pressure outlet? How did you decide on this?

By the way, shouldn’t there be a void inside the solid body, so that the air passes through?

Best regards,
Fillia

Hello,

The outlet pressure on the fluid domain is 23842Pa, this is just the static pressure at an altitude of 10670 m.

I thought i wont require making a void inside the solid body as i only wanted to simulate the inlet area. I will try and simulate it with the void however, i would require a mass flow at the fan. Is it possible to define a boundary condition on the fan where the fan would not be a solid body but a fluid acting like a fan suction.

Regards,
Syed

I see, keep in mind that this fixed value should be the total pressure.

And If I understand your question correctly, then you could define a momentum source inside the fluid to add acceleration:

Hi

There should not be a void inside the solid body just a fan plate with a specified pressure outlet boundary condition.

here is the project file: https://www.simscale.com/workbench/?pid=1748814654388204345&mi=run%3A49%2Csimulation%3A24&mt=SIMULATION_RUN

run case 19 (higher velocity) is the error i am getting

Hey there,

Perhaps ramping up your inlet velocity from zero to the max value over a number of iterations (say 500) could help with the convergence in the compressible simulation.

This is showcased in the following tutorial:

hi,

i assume i would do it like this:

Yes, please try it this way.

Hello i have received the same error.

here is the project link https://www.simscale.com/workbench/?pid=1748814654388204345&mi=run%3A51%2Csimulation%3A24&mt=SIMULATION_RUN

I assume you already did this, bust at least for the record, please follow the guidelines given in this article:

Hi,

Yes i have gone through this and i have read it again. I see the mesh quality is good and have no bad mesh.

Still confused as to why this is diverging.

I have looked at some literature which have similar setup to my one.

Here are other peoples literature: https://fenix.tecnico.ulisboa.pt/downloadFile/1407770020545214/Bruno_Conceicao_64957_Thesis.pdf
From page 36 onwards

Hello,

If I may ask, what is the purpose of this boundary condition, specifically?

A pressure outlet generally represents fluid going out of the system (in this case, it would mean flow entering the inner part of the rocket, which doesn’t make a lot of sense). If you pay close attention to the divergence region, it’s always very close to this face in particular.

I’d suggest reviewing the boundary conditions, in particular “Pressure outlet 6”, which seems to be causing problems.

Cheers

Hi

The reason for this boundary condition at the fan plane is for simulating how a fan would act if it was simulated. For my project i wont require simulating the fan, core or exhaust of the engine as the main area of focus is the inlet of the turbofan.

From literature, someone placed a pressure outlet boundary condition at the fan plane.

From page 36 onwards

Regards,

Syed

Hi!

Removing that boundary condition (or at least replacing it with a more fitting option) would be a good idea. With the current settings, we are defining a pressure outlet to a face that we know for a fact that will act as an inlet.

To me sounds very unconventional (and it also causes the simulation to break, since we a lot of backflow).

Cheers