high simulation time - model failiure or normal?

[Anonymous]

Hi,

first of all two information:

- english is not my mother language so please excuse linguistic mistakes. 

- I've not worked with CFD very often and may ask dumb questions

The simulation goal is an appraisal of the cooling power of liquid flown aluminium pipes in an air stream. (140 small pipes, wooden box with in- and outlet to define the air strem parameter, mesh parameter 3371961 knots and  12426536 elements, stationary simulation, cloud solver, 1000 iterations).

Unfortunately the result download failed after a simulation time of 71 hours. Now I've started the simulation run once again.

My main question: is the simulation time "normal" or do you think I chose strange/wrong boundary conditions/produced some model failure?

Thank you for your help.

Kind regards,

Jonas

[Anonymous]

Hi @Anonymous,

thank you for your quick answer. Unfortunately I've modified the the model before starting the new run (61 hours ago). So I can not answer your question.

Jonas

[Anonymous · Accepted solution]

@Anonymous 

You said: "Unfortunately the result download failed after a simulation time of 71 hours." 

Sorry, I didn't notice that you also mentioned that you're running in CLOUD.

So if you're running on the cloud you can't be running a simulation for more than 72 hours.

Please, if this answers your question, mark as solution.

[Anonymous]

Hi @Anonymous,

I am using the CLOUD to solve the simulation.

I've created an cfz file but can not attach it to this answer. How can I share it with you?

Thank you very much!

Jonas

[Anonymous · Accepted solution]

Hi @Anonymous 

If you're using the CLOUD then you can't be running a simulation for more than 72 h.

I think that you might have to divide your iterations. For example, run 200 iterations on CLOUD and after you get the results, run again on cloud but select "Continue from: 200".

You might have to upload it to dropbox and share by link.

See this:

https://forums.autodesk.com/t5/cfd-forum/runtime-limitations-in-cloud-no-result/td-p/8200960

[Anonymous]

Thank you for your help and I think this would be a very good option in case the model is ok.

Under the following link you should be able to download the CFZ file:

https://rubde-my.sharepoint.com/:u:/g/personal/jonas_claus_rub_de/EXlgVfQZeIxOn7jXds-uopwB49vuKuxvWz...

[Anonymous]

Can you simply share a screenshot of your geometry + grid? 12m could be oversized

[Anonymous]

Hi @Anonymous  @Anonymous ,

Jonas, the best guy to analyse the mesh is Vonkarman 😉 But I don't think 12 M elements are too much, considering that you have a lot of tubes and the size of the model.

@Anonymous please confirm if I'm correct:
First of all, I don't actually know why your inlets and outlets of the 140 tubes are a square... 

Also, you are not considering natural convection inside the box. 

You should disable ISC (Intelligent solution control) and are you sure about using Turbulence and auto forced convection?

[Anonymous]

@Anonymous: I created the in- and outlets as surfaces while constructing the inner volume. Is there a possibility to change the sharp to a circle?
I didn't think to much about aktivating tubulances and natural convection. I see why to deactivate the natural convection. But isn't it meaningful to consider turbulances? I guess they are high relevant for the heat transfer near the pipe surface.

@Anonymous 

I hope this picture is meaningful. It is the same geometry from another simulation run. I used the auto mesh function to create the mesh. As I said initially, I am not to versed in the use of Autodesk CFD.