# Errors with table velocity input?

**URL:** <https://www.simscale.com/forum/t/errors-with-table-velocity-input/84755>\
**Category:** Project Support\
**Created:** [March 16, 2019, 12:49pm UTC](https://www.simscale.com/forum/t/errors-with-table-velocity-input/84755 "2019-03-16T12:49:41Z")\
**Posts on this page:** 1\
**Showing post:** 9

<div class="post-metadata">

**Author:** ![badio93](https://www.simscale.com/forum/user_avatar/www.simscale.com/badio93/32/23264_2.png) [@badio93](https://www.simscale.com/forum/u/badio93)\
**Post date:** [March 16, 2019, 3:54pm UTC](https://www.simscale.com/forum/t/errors-with-table-velocity-input/84755/9 "2019-03-16T15:54:44Z")

</div>

I found the answer in Darren’s post.

“between points defined as X, Y, Z the velocity will be linearly interpolated, so it is important that good resolution is given close to the 0 velocity edge, furthermore, several ‘poles’ of points are recommended. i.e. if the inlet boundary was in the YZ plane normal to X, and Z low was the floor, a CSV where Z varies for example [0.01, 0.02, 0.04, 0.08, 0.16, 0.32, 0.64, 1.28, 2.56…] and Y varies [-200, -100, 0, 100, 200] giving poles of points at -200m etc in the increasing distance from the ground if the ground was located at Z=0.”

So, taking a look to the csv example posted by Darren next to the quoted part …all the vectors that i define should have starting coordinates related to plane position in global reference, said so, if my inlet XZ plane finds at Y=-800, all my vectors should have Y=-800 on table.  
And, to have a more accurate simulation all along the width of the wind tunnel, it may not be enough to create only one “vertical line” of starting points on the plane…in this case, i should create more vectors vertical “groups” changing X coordinate while keeping, of course, Y fixed.  
In the end, all the vectors that share the same altitude, will have same Uy value.

Made a test and in fact wind profile look finally realistic, with velocity inlet values increasing with altitude.  
Used three interpolation sets of points, at X=300 X=0 X=-300, with Y constant=-800, which is the coordinate of my inlet face in global axis reference.

Hope it will help other construction designers 🙂

 ![1](https://www.simscale.com/forum/uploads/default/original/3X/0/9/09ea69154097b761a452b809a508f32cf4a8dd89.jpeg)

---

_[View the full topic](https://www.simscale.com/forum/t/errors-with-table-velocity-input/84755)._