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Old   April 20, 2017, 01:18
Default New Ansys User
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Hi.

I am a final year university student from Malaysia doing a project using Ansys Fluent.

So I have a 2D model size 20m x 30m with a cylinder diameter of 1m. I have run some simulation using water as the liquid, velocity of 80, and using transition SST. The result I get is not good. The cl and cd are not acceptable. Also there are no vortex form behind the cylinder.

Is my setup wrong or something?

Can anyone help me with this?

Thank you.
Arif.
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Old   April 21, 2017, 11:25
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Fernando Avelino
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The initial simulations can be frustating sometimes...

These checks may help:
- Is your mesh properly refined where it needs to be?
- Have you tried another models? (A complex model does not mean always the best results.)
- Have you studied the parameters of chosen model? Are they properly set?

Regards.
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Old   April 22, 2017, 00:31
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Hi godeny_mecaer.

Thank you for your time replying this.
I did all the checks that you suggested but the results is still not acceptable.
And yeah it is frustrating doing this simulation for the first time.

Can you help me set a model that is properly set so I can try do the simulation using it?

Regards,
Arif.
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Old   April 22, 2017, 15:49
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Fernando Avelino
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Quote:
Can you help me set a model that is properly set so I can try do the simulation using it?
Hi Arif.

I had this very same question when I was starting my project. My advisor just said: "It's not that easy to choose a model. You must define the parameters that will be important and which will be neglected. Then, do various tests with various models and compare the results with experimental or reference data". At first time, it sounded useless. In fact, I've learned a lot. For example:

- The mesh refinement has much more impact on the model than it appears. Almost all models have a minimum mesh refinement acceptable to work properly, but there are some models with a maximum allowable refinement.

- Sometimes a simulation requires much more iterations to converge than expected. A more refined mesh and/or more complex model increase significantly the iterations calculated before the simulation starts to converge.

In other words, this initial stage is, basically, trial-and-error. It's a boring, but important, process and you'll need a little patience to deal with it.

Good luck!
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