# Determine and plot the superficial velocity
**URL:** https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441
**Category:** ParaView Support
**Created:** [February 11, 2021, 11:31am UTC](https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441 "2021-02-11T11:31:04Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Sumit\_Zanje](https://discourse.paraview.org/u/Sumit_Zanje)
#### Post date: [February 11, 2021, 11:31am UTC](https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441/1 "2021-02-11T11:31:04Z")
Hi,
I’m performing pressure driven flow in the horizontal pipe using OpenFOAM. As the case is pressure driven flow, it gives specific velocity of liquid based on pressure difference between upstream and downstream end of the pipe. Once the flow is developed, air is introduced from upstream end and this gives flow transition from stratified to slug flow on so on.
Now I can plot the velocity at any point using probe in paraView. But I’m interested in the plot of superficial velocity of gas Vs Superficial velocity of liquid, which are different than the velocity of gas and velocity of liquid.
Please find attached link for further details;
> **[5.%20Multiphase%20flow.pdf](https://ocw.snu.ac.kr/sites/default/files/NOTE/5.%20Multiphase%20flow.pdf)**
>
> 3.97 MB
It would be great if some one can assist me on this.
Regards
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [February 14, 2021, 5:21pm UTC](https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441/2 "2021-02-14T17:21:20Z")
Is the diameter of the pipe uniform? If so, you can use the `Calculator` filter to divide the specific velocity by the known cross sectional area of the pipe.
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### Author:  [@Sumit\_Zanje](https://discourse.paraview.org/u/Sumit_Zanje)
#### Post date: [February 22, 2021, 8:36pm UTC](https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441/3 "2021-02-22T20:36:42Z")
> [@Kenneth\_Moreland](#):
>
> r to divide the specific
Hi, Thanks for the response.
Yes, pipe diameter is constant (say, 6" pipe). Could you please elaborate more?
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### Author:  [@Kenneth\_Moreland](https://discourse.paraview.org/u/Kenneth_Moreland)
#### Post date: [February 22, 2021, 9:13pm UTC](https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441/4 "2021-02-22T21:13:45Z")
1. Load your data as you already are.
2. Select the `Calculator` filter 
- It’s conveniently located on the third toolbar all the way to the left.
3. In the properties panel, change the `Result Array Name` from “Result” to something meaningful (such as SuperficialV). (optional)
4. Set an expression (in the text box right underneath the `Result Array Name`) to the math expression you want. For example, if your specific velocity is in a variable named `SpecificV` and the constant radius is 6, you might set the expression to be `SpecificV / 6`.
- You can use the buttoms and scalar/vector combo boxes right below to help you build the expression.
5. Hit `Apply`.
If you need more information, the calculator filter is featured in [many ParaView tutorials](https://www.google.com/search?q=paraview+calculator+filter).
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### Author:  [@Sumit\_Zanje](https://discourse.paraview.org/u/Sumit_Zanje)
#### Post date: [February 22, 2021, 10:22pm UTC](https://discourse.paraview.org/t/determine-and-plot-the-superficial-velocity/6441/5 "2021-02-22T22:22:20Z")
Thanks.
I will get back to you after trying your suggested approach.
Regards