# Radial and tangential velocity

**URL:** https://discourse.paraview.org/t/radial-and-tangential-velocity/15039
**Category:** ParaView Support
**Created:** [July 11, 2024, 11:15am UTC](https://discourse.paraview.org/t/radial-and-tangential-velocity/15039 "2024-07-11T11:15:04Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Il\_Briga](https://discourse.paraview.org/user_avatar/discourse.paraview.org/il_briga/32/14763_2.png) [@Il\_Briga](https://discourse.paraview.org/u/Il_Briga)
#### Post date: [July 11, 2024, 11:15am UTC](https://discourse.paraview.org/t/radial-and-tangential-velocity/15039/1 "2024-07-11T11:15:04Z")

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Hi to everyone,

Very silly question here. But i have not found a proper answer yet. Given the velocity profile in the coordinate direction (U\_X, U\_Z) over a plane XZ plane, with Y normal, (i.e in my case a slice of an annular duct) i have to compute the radial and tangential velocity. Is so right the following procedure?

1. Compute the angle alfa with the phyton calculator as suggested here [quote=“Kyoshimi, post:2, topic:12796, username:Kenichiro-Yoshimi”]  
`arctan2(points[:,2], points[:,0])`  
[/quote]. In my case i put [:,2] since the coordinate is along the Z direction;

2. Estimate the following scalars simply using the calculator `U_rad=U_X*cos(a)+U_Z*sin(a);` and `U_tan=U_Z*cos(alfa)-U_X*sin(alfa);`. Where U\_X and U\_Z are scalars too.

Have i to add something else (e.g the coordinate results as option)? Or must i consider the vectorial product (e,g including IHat and kHat)?

I know it’s a trivial question but i want to be sure of this.

 ![alfa](https://discourse.paraview.org/uploads/default/original/2X/2/29b56a9e2676dcda9cc4c2e164ca6130bb0bf896.png)  
 ![UX](https://discourse.paraview.org/uploads/default/original/2X/1/11aff282376df40a7a8095d33bc866f7b4d6191e.png)  
 ![UZ](https://discourse.paraview.org/uploads/default/original/2X/8/89de25ab0eb7e6b00ef2858098f8a255db25b2f4.png)

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### Author: ![FEngineer](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/f/5f8ce5/32.png) [@FEngineer](https://discourse.paraview.org/u/FEngineer)
#### Post date: [July 12, 2024, 9:02pm UTC](https://discourse.paraview.org/t/radial-and-tangential-velocity/15039/2 "2024-07-12T21:02:14Z")

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Check this thread: [Polar Velocity components - #2 by FEngineer](https://discourse.paraview.org/t/polar-velocity-components/13786/2)

And please also upvote the feature request mentioned there if you’d like to be able to do it with built-in tools.