[tusin111]

hello!
I'm new to openFoam!

Currently, I want to solve the turbulence problem by making a simple model in snappyhexMesh, but I can't converge!

So, I have a few questions for you!

In k-epsilon turbulence, is the initial condition and the mesh influencing the convergence correct?

If that is correct, is it correct to obtain k and epsilon according to the formula below?

Also, is the smaller the size of the mesh, the better the convergence?


As shown in the picture below, after obtaining the initial conditions of k and epsilon, I analyzed
It repeats between residual 0.01 and 0.001 and does not converge..!!

please give me some advice!!

[amirhosseintaran]

Originally Posted by tusin111

hello!
I'm new to openFoam!

Currently, I want to solve the turbulence problem by making a simple model in snappyhexMesh, but I can't converge!

So, I have a few questions for you!

In k-epsilon turbulence, is the initial condition and the mesh influencing the convergence correct?

If that is correct, is it correct to obtain k and epsilon according to the formula below?

Also, is the smaller the size of the mesh, the better the convergence?


As shown in the picture below, after obtaining the initial conditions of k and epsilon, I analyzed
It repeats between residual 0.01 and 0.001 and does not converge..!!

please give me some advice!!

Hi Jinhoon,

Answering to these general questions are quite impossible even for CFD specialists, So I would like to suggest that try to tell me more about your problem, maybe geometry or sth like that.

[tusin111]

Originally Posted by amirhosseintaran

Hi Jinhoon,

Answering to these general questions are quite impossible even for CFD specialists, So I would like to suggest that try to tell me more about your problem, maybe geometry or sth like that.

thank you for the reply!!

I would like to analyze the shape attached below by removing air through suction!

Currently u,v,p ,epsilon ,k are
It is the result of convergence down to 1.e-4, but the result is a little different from what I thought, so it seems wrong!

In particular, in the suction part, the fluid is strongly sucked in with y+, but looking at the movement of the fluid, there is a part that goes to y-, so it is questionable!

Can you tell me what is the problem??

I will attach my initial condition, fvsolution and fv scheme!!

Please let me know if you need more information!!

[tusin111]

Originally Posted by amirhosseintaran

Hi Jinhoon,

Answering to these general questions are quite impossible even for CFD specialists, So I would like to suggest that try to tell me more about your problem, maybe geometry or sth like that.

Enter more information!!

[peterhess]

Your outlet channel is very short and you will most likely have a back flow.

The velocity at the outlet defined to be zeroGradient.

Generally it is a good idea to have inletOutlet BC for the outlet.

See chapter 1.51 for more details.

https://www.nextfoam.co.kr/proc/Down...tions_of41.pdf

Also you can try increase the length of the channel to give the flow the chance to overcome the backflow.

You also could need to define the backflow velocity in inletOutlet.

And define also the turbulence properties of the backflow could help overcoming the problem.