# How to plot pressure and force of single (or multiple) points on a patch over all time steps?
**URL:** https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035
**Category:** ParaView Support
**Created:** [May 7, 2023, 7:34am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035 "2023-05-07T07:34:45Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 7, 2023, 7:34am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/1 "2023-05-07T07:34:45Z")
Hi
I have a multiphase case (VOF) and simulated it using interFoam. Using ExtractBlock filter I have selected a patch I need and I have got the patch normals using GenerateSurfaceNormals filter.
My first question is how to define the force on the patch using the calculator filter. Does “p\*Normals” work and give the force vector in Newton? I understand that the force is pressure times area, but I cannot see how to multiply pressure by the patch cell area and integrate it over the patch to get Fx and Fy.
Moreover for a single point on the patch, I need to plot the force x and y components and pressure over all time steps. How can I use filters to do it? Any help is greatly appreciated.
Cheer
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 9, 2023, 9:47am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/2 "2023-05-09T09:47:09Z")
Hi @A_E
> Does “p\*Normals” work and give the force vector in Newton?
ParaView doesn’t know anything about your units, it is just doing the math computation that you are asking for.
> I need to plot the force x and y components and pressure over all time steps
Plot data over time
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### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 23, 2023, 9:20am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/3 "2023-05-23T09:20:09Z")
Hi Mathieu
Thanks very much for your response.
So I need to calculate the force making sure about the units which is fine but could you please let me know how I can get the patch cells area to integrate my calculations over the patch?
Re plot data over time, my problem is that I cannot select the points I need so that I can plot the point data over time. I have clipped and sliced my patch to get a line and I would like to select a point on the line and plot the results for that point over time but I couldn’t get it to work.
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 23, 2023, 9:21am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/4 "2023-05-23T09:21:31Z")
> [@A\_E](#):
>
> I cannot select the points I need so that I can plot the point data over time.
Create the geometry of the point you want to extract, then use ResampleWithDataSet.
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### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 23, 2023, 9:28am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/5 "2023-05-23T09:28:43Z")
Thanks, so you mean to use Point Source filter on the line I have got and then Resample With Dataset filter and then Plot Data Over Time?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 23, 2023, 9:32am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/6 "2023-05-23T09:32:17Z")
That is one way to do it, yes. It would be easier to read a line from a file if it is already defined somewhere. A simple .csv + TableToPoints would do the trick.
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### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 23, 2023, 9:37am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/7 "2023-05-23T09:37:21Z")
Okay thanks. I’ll give them a go. My patch is a bit complex so a bit hard to get the point coordinates but I guess the way you said is good if I can define points in a .csv file somehow.
Cheers Mathieu
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### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 23, 2023, 9:38am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/8 "2023-05-23T09:38:58Z")
And I assume there is no way we can use patch cell areas in our calculations?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 23, 2023, 9:40am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/9 "2023-05-23T09:40:10Z")
You should be able to compute the cell areas first, then use that in a calculator or python calculator.
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### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 23, 2023, 9:59am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/10 "2023-05-23T09:59:25Z")
How can I do the cell area? Could you demonstrate please? Do I need to use a code?
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### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [May 23, 2023, 10:00am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/11 "2023-05-23T10:00:49Z")
Use CellSize filter.
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### Author:  [@A\_E](https://discourse.paraview.org/u/A_E)
#### Post date: [May 23, 2023, 10:03am UTC](https://discourse.paraview.org/t/how-to-plot-pressure-and-force-of-single-or-multiple-points-on-a-patch-over-all-time-steps/12035/12 "2023-05-23T10:03:46Z")
Awesome, thank you! I’ll check all what you told to get a result