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Old   June 5, 2024, 22:26
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Hello all,


I've made a streamtube in paraview following the steps from this post: Stream tube visualization


Is there a way to calculate the cross-sectional area of this streamtube as a function of x? Also, is there a way to extract data that is enclosed within the streamtube?


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Old   June 9, 2024, 04:41
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Cross-sectional area: not sure how to get that, but first I am interested what your tubes look like? I assume most people use a fixed radius thus have constant area at each position of the steamline?


Get data from "inside": most of the filters in ParaView have more than one representation. Usually to get to the data, you can just open a Spreadsheet View (instead of a new render view) and activate the tube filter from the tree and see if it shows you any data. If it does, it is probably the data "inside" the tubes. You can export that to csv for example.
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Old   June 9, 2024, 15:17
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Thanks for the reply.


My streamtube doesn't have a constant radius as I have it placed near a spatially varying heat source. Before the heat source the cross sectional area is constant, but around the heat source the streamlines are deflected which changes the cross sectional area of the streamtube.


Haven't been able to get the data from inside the streamtube, but thank you for your suggestion I will try that. I have tried to use the extract enclosed points filter but it returns points that lie outside of the streamtube.
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Old   June 10, 2024, 10:34
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Can you show an image of that? Steam tubes are a way to show stream lines in a "thickened" way, I assume ParaView just thickens up the line perpendicular to the local longitudinal direction of the line, making it uniform in thickness at all points. It feels like we talk about different things.
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Old   June 10, 2024, 11:25
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Sorry about the confusion. I've attached 2 images of the streamtube
Attached Images
File Type: png Picture1.png (58.2 KB, 5 views)
File Type: png Picture2.png (136.1 KB, 9 views)
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Old   June 11, 2024, 05:46
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So we talk about different things all right. A stream tube is one of those "lines" there. You seem to be looking for the volume enclosed by the "virtual surface" formed by the streamlines?
First, no idea how to get that, second but more importantly: why do you need that? What is your goal?
The enclosed volume you seem to be looking for depends on where you spawn your streamlines (seed points). I cannot think of a way to get meaningful output of what you are trying to do.
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Old   June 11, 2024, 11:55
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I'm a bit confused, I thought the lines were the streamlines and the streamlines form the streamtube. What I am trying to do is compare the results of my simulation to a quasi-1D flow model with heat addition that I am developing.
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Old   June 12, 2024, 03:51
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A stream tube in Paraview is just a streamline thickened by a certain amount to give it a 3d appearance.
What you think of as stream tube, no idea what to call it - the main flow space? A jet? Anway, the space that is contained by the stream lines in your image is arbitrary and depends on where these streamlines are seeded. I don't know what method you used to create the seed points? Are they on a line?
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Old   June 12, 2024, 12:50
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I seeded the points on a circle by creating an ellipse source with a radius ratio of 1. I then used the mask points to filter to sample points on the circle, which I used as the seed input to the stream tracer with custom source filter.
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Old   June 13, 2024, 02:01
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Yeah and if you change the settings of the seeding, you get another volume of what you call "stream tube" ... so I still do not understand why you need that volume. It has no physical meaning, for a given flow it just depends on where the seedpoints are located.
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