Wrong Result?
 

I am modeling 2D airflow passing an aerofoil inside the wind tunnel in the Fluent and Gambit.

The geometry is, the wind tunnel is as a rectangle.

However, when I see the animation, the flow of the wind is like the flowing inside a closed area and trapped.

It flows rotating around inside the rectangle.

What happened?

How to solve it?

Change the type of the boundary?

I also read "reversed flow in outlet"

Thank you

some pics please ...

This is the picture.

Unfortunately, I can not watch the animation anymore because the display window is becoming blank and black when the iteration process is running.

The problem occurs too when I playback the animation.

Only if I know how to fix the blank-and-black screen problem, I will attached the animation file as a movie instead of a picture.

specify symmetry condition on side, top and bottom walls.

The model in test section is airfoil or cylinder?

Which side I should specify as a symmetry?

Right side, left side, or both?

This is the image of the contour of the vorticity magnitude when I change the boundary conditions of the top edge and the bottom edge from velocity inlet to symmetry and keeping the left edge as a velocity inlet and the right edge as the pressure outlet.

Still have the "reverse flow in the outlet" message.

I still can't upload the movie because of the blank-and-black screen problem.

Actually it's a cylinder.

Both sides and also top and bottom wall be specified as symmetry.

This is the display of the contour of the velocity magnitude when the boundary conditions of the all edges of the rectangle were changed to the symmetry.

All BC changed to Sym :o I hope you are not talking about inlet and outlet.

The results in contour plot are from fully converged solution? If not run it for longer duration.

Yes. All BCs were changed to sym.

The original BCs before they were changed are:

left edge: velocity inlet
right edge: pressure outlet
top edge: velocity inlet
bottom edge: velocity inlet

I compute it from the left edge to the right edge.

The wind is flowing from the left side to the right side.

The left edge should be as the inlet and the right side as the outlet.

No.

The contour is displayed before the iteration process.

As I was already told you, I have a problem and the problem is the display become blank-and-black when the iteration is processing.

This is the reason why I can't upload picture or animation after fully converged.

From left to right flow this should be the BC:

left edge: velocity inlet
right edge: pressure outlet
top edge: symmetry
bottom: symmetry

Are you saving frames to do an animation? Are they still blank?

No but once it works.

However, now isn't working anymore.

Yes.

The display window of the animation is blank-and-black too when I playback the animation after fully converged.

Are you running a steady or a transient case?

Are you following the steps at calculation activities/solution animation tab and selecting the contour you want with the frequence you want?

I think you should get the simulation right first, and once it's okay set an animation in the calculation activities/solution animation tab.

Well, I check the steady option under define > models > solver.

I think you should see one of the image I already uploaded in this thread.

Clear it says Fluent 6.2.16.

Calculation activities is available in ANSYS 12, am I right?

I think you should read the entire posts inside this thread before posting your message.

It's clearly written:

"I can not make the animation/simulation because the display window is become blank and black (or I would just say become blank without black because the background color can be changed from black to white), nothing is displayed in this display window, when the iteration is start processing."

I've read your post completely before posting. But I don't know how you are defining your animation step by step.
When I do a simulation, normaly a time-dependent case, I wait until the case is converged and then I record the animation.
I was suggesting you put BC right, let the case run, and then set the animation.

From this I guess you want a convergence animation rather than a time animation, right?
I'm not sure about that, but in Fluent 6.2 there should be an option Solve/animate/define or something similar to select the frames and frequency.

Remember I'm just trying to help you. Good luck.

Well, any of them is fine.

Yes.

I set the animation in the Solution Animation window (Solve > Animate > Define).

But I am not sure of the frames and frequency you're talking about.

Maybe in the Solve > Animate > Playback.

Frames is the start frame, increment, and end frame.

Frequency is the replay speed such as within the slow to fast range.

Is it correct?

If you want to the see the flow time evolution it must be a transient case.
If you want to animate how aproximate solutions are getting to the converged one, it should be a steady case.

First, in a menu like the one in picture 1 you should select how often you want to save a frames, every X iterations or timesteps (in the transient case). In define you go to menu in picture 2. You select what exactly want to be recorded. Specify a name and a folder and save.

Then the simulation is run and you'll get a frame recorded in the specified folder every X iterations/timesteps. Do you have this files in your case?

Once it's finished you can play it in the menu like the one in picture 3.

I don't know if you have followed all this setps and the problems persists.

In fluent users guide (ansys 12) all this is explained in 26.16 Animating the solution.

You may find some usefull tutorials here:
https://confluence.cornell.edu/displ...arning+Modules

I know there are two options in the When drop-down menu, time step and iteration, in the Solution Animation window.

But why there is only available iterate option under the Iterate window, and it's different as the second image.

These pictures are from the run calculation menu?

The first one looks like the steady simulation iterations panel, no timesteps in a steady simulation.
The sencond one is to set up the transient simulation iterations. You can choose how many iterations per timestep, how many timesteps and the size of the timesteps.

This is to set the iterations of the solver, nothing to do with animation.

that screen turning black is a mystery...

Spincfd,

Have you checked which window the data should appear in? You should find it in monitors window. Make sure you choose the same window as specified in the monitors tab and "Print to console" is activated. Otherwise you may have the blank window.

OJ

How to do the transient iteration?

Go to general tap (on left side) and choose transient. Now go to calculate panel and give the time step size and total time steps.

This is the video of the blank screen problem.

http://speedy.sh/7mpVt/Video.zip

I am sorry as the video resolution is too small and can not be viewed.

I am trying to upload better video resolution.

It doesn't looks like Fluent 6.2.16.

Also, it looks like you are using a Mac.

Compare yours with mine.

Go to the general tap?

Perhaps tab.

There is no general tab in Fluent 6.2.16.

Define - Model - Solver
Where you see Time choose unsteady (unsteady - transient means the same)

http://cdlab2.fluid.tuwien.ac.at/LEH.../tg/node57.htm

You can find this in Solve - Monitors - residuals
See step 4 here:
http://cdlab2.fluid.tuwien.ac.at/LEH.../tg/node61.htm
On the top right corner, in Plotting square you can choose the windows where to show your monitors.

Be sure you are recording each frame of your animation, you will have a file for each one. If you don't have this you might have not set the animation properly and that why you can't watch it.

Fluent 6.3 User Guide: http://cdlab2.fluid.tuwien.ac.at/LEH...g/main_pre.htm
Fluent 6.3 Tutorial guide: http://cdlab2.fluid.tuwien.ac.at/LEH...g/main_pre.htm

Why I should choose the unsteady if I want the steady and laminar flow?

What I understand is, you tell me to check/choose the unsteady option if I want to iterate as a time step instead of number of iteration, am I right?

I don't do this step before the blank problem appears but the display shows the animation very good.

I have a laptop, the blank display also happen in my laptop.

I can see all of the files associated with the animation for every frames.

A lot of files.

Yes.

Can you open any of this files to check if they're okay?

There are two types of file.

.hmf and .ppm

What software to open them?

And how do I know if them is okay or not?

ppm are portable pixel map. I've opened them with photoshop, but I'm sure there are other softwares.

With correct I mean if there's something on those images or they're blank.

I open one of them, the .ppm file, in the Adobe Photoshop and you are absolutely correct.

The image shows blank.