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Plotting velocity profile

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Old   August 19, 2014, 07:27
Arrow Plotting velocity profile
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Hi everyone,

I'm new to Ansys so excuse me for the noob question.
First thing I've tried with Ansys is analysing a 2D flow in a channel. I want to find the Length of the channel for which the flow is fully developed. I've done some calculations and eventually ended up constructing a geometry which I think will allow a fully developed flow, considering my Reynolds number (it's a laminar-viscous flow).
Now, I want to plot the velocity profile downstream, and see if my profile is indeed fully developed. What I've done is I went to the XY plot and created a line which has a downstream X coordinate, and a Y coordinate going from 0 all the way to the upper wall. I expect to get a parabolic profile, yet I keep getting the profile attached. It's obviously not plotting the change of velocity in respect to Y, rather, it's plotting the change of velocity in respect to X (you can see the graph starts at X=0.213 which is my designated X coordinate, not Y, and goes all the way to the Outlet and beyond).

What am I doing wrong???
Thanks in advance
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Old   August 19, 2014, 08:23
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Change the plot direction to 0 1 0 and also check the correct definition of your line visualy.
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Old   August 19, 2014, 08:37
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I did try to change the plot direction to 0 1 0, but it's still wrong...
How can I check the definition of my line visually?
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Old   August 19, 2014, 08:43
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Display it via the display mesh function.
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Old   August 19, 2014, 08:55
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Right, yeah, my line is correct.
I think I understand what the problem is.
When I change the plot direction to 0 1 0 is actually does give me the right velocity profile, only it's half of it. My channel height is 0.009 x 2, but when I put my Y coordinates as -0.009 to 0.009 it only plots from 0 to 0.009, and forgets about the rest. I tried creating two lines, one from 0 to 0.009 and one from -0.009 to 0, but I get an error message on the second line ("surface creation failed"). It's probably because I've done my analysis on half a channel (0 to 0.009) and then mirrored it through the center line. DOH! How can I mirror my half plot then?
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Old   August 19, 2014, 09:45
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I do not know if this is doable in Fluent. You can do a little workaround by writing the plot data to a file (check option write to file) and mirror the data manually in an external software like calc, excel, ... and then load it in Fluent.

Another option: Monitor an other flow variable. For a fully developed flow the derivative of velocity in flow direction should be zero. Plot the derivative in flow direction and check where it becomes zero.
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Old   August 19, 2014, 10:04
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I've used excel and it works perfectly.

Thanks kad, you've been very helpful!
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Old   August 19, 2014, 11:00
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From your first screenshot I can see that you are using the axisymmetric option.
This requires (or at least implies) that your entire model lies above the x-axis.
The x-axis is assumed to be the axis of symmetry in fluent by default.

So there might be something wrong with your setup if the extent of your computational domain ranges from -0.009m to 0.009m in y-direction.
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Old   August 19, 2014, 11:29
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The domain is fine. I've build my channel from 0 to 0.009 above the x axis, and after getting results I used Display>Views>Mirror Planes>Centerline to mirror the graphic results. It's just the XY plot that didn't work.
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