[McCharles]

Hello everyone,

i was wondering what a Streamline plot actually does? In cfd post i have to choose a plane to plot the streamlines. It makes no sense to me because the streamline of a particle is 3 dimensional, so what are the continuous lines i see over the selected plane?

Thanks in advance,

Charles

[HenningW]

Those lines on your screen are most likely pixels. - Sorry, I could not resist :P

But now let's get serious. Without any further information it is hard to answer you. What is your case, what post processing tool did you use and what were your steps might be a good start. Maybe post a few pictures of the results we are talking about.

Out of the blue it is almost impossible to give you a proper diagnosis. Just an assumption: Either that plan is used to set the seeds or it only uses the elements of the vector that run parallel to the plane.

[Tobi]

The lines that you see are finally the trajectories of the flow. If you plot them and turn on the glyphs, you will see, that they are similar. In other words, if the flow field is steady state and you would put a particle on the start of one path-line (trajectory), the particle will flow through the domain as indicated by the streamline / trajectory.

It does not matter which post processing tool you are using. A streamline is a streamline and finally it is a trajectory of the flow.

If you make a slice and use the filter, the lines correspond to the trajectories on that plane. If the trajectory is a 3d line, it could also be possible that some parts are align within that plane. These parts you see. Simple check -> motorBike tutorial.

[HenningW]

I agree with Tobi.

Just to be clear, since my post might have been slightly missleading:

The way the streamlines are calculated is (almost) independent from your Software.

The presentation might vary though. Paraview should end the streamlines the moment your flow leaves the slices, when you used the slice as the base for your streamlines. If you used your volume, it should present the streamlines independent from your slice.
However, if your flow is 2D anyway, it should be shown perfectly fine in the slice as well.

In cfd post i have to choose a plane to plot the streamlines

Do you mean you Chose the plane to define the seeds or did you want to present your streamline in one plane. The second one would be a weird way to do for a 3D flow, though.

Again, at least for me, it is hard to figure out exactly whats going on, without knowing the steps you took in your post-processing. Sometimes ist just a wrong reference in your Project tree, if you use paraview.

[McCharles]

I am using cfd-Post from Ansys to do the post processing. I can either Display the path of a particle in 3D and to me that is absolutely comprehensible, or plot a streamline over a fixed plane, like the XY-Plane. The flow I am simulating is higly turbulent and 3-dimensional. Nonetheless cfd-Post displays clear streamlines over every selected plane. Unfortunately I can't upload any pictures of the geometry I am using but the flow type corresponds to a Taylor-Couette-Poiseuille flow in a conical gap, similar to this :

https://de.wikipedia.org/wiki/Taylor...,_animiert.gif

If I select the 2D-Streamline plot in meridional direction, cfd-Post will show something similar to this :

https://de.wikipedia.org/wiki/Taylor...s_Re%3D950.png

which is also a 2D Stream-Plot of a 3D flow.

I have difficulties to understand what those lines represent in relation to the plane, maybe some kind of trajectory projection?

Cheers,

Charles

[HenningW]

A projection seems possible. Maybe try to put a 3D streamline on the surface and look on it perpendicular. the lines should coincidence in that case.

Another possibility that comes to my mind: It might be that the program just ignores the component in the direction perpendiculat to the surface.)

Usually the help in Ansys is a great source for help, have you had a look in there?
Also you might want to try the ANSYS Forum here to ask that question. I assume that there will be more users familiar with the software than in OF-Post

[McCharles]

Good idea, I will give it a try.

Thanks for your help.

Charles

[mahdi-united]

Originally Posted by Tobi

The lines that you see are finally the trajectories of the flow. If you plot them and turn on the glyphs, you will see, that they are similar. In other words, if the flow field is steady state and you would put a particle on the start of one path-line (trajectory), the particle will flow through the domain as indicated by the streamline / trajectory.

It does not matter which post processing tool you are using. A streamline is a streamline and finally it is a trajectory of the flow.

If you make a slice and use the filter, the lines correspond to the trajectories on that plane. If the trajectory is a 3d line, it could also be possible that some parts are align within that plane. These parts you see. Simple check -> motorBike tutorial.

hi
what is the difference between pathline's outlet in results of FLUENT and streamline in CFD_post?