# Incoming flow with an Angle of attack

**URL:** <https://pyfr.discourse.group/t/incoming-flow-with-an-angle-of-attack/799>\
**Category:** Cases\
**Tags:** compressible\
**Created:** [17 April 2023 15:56 UTC](https://pyfr.discourse.group/t/incoming-flow-with-an-angle-of-attack/799 "2023-04-17T15:56:21Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\
**Post date:** [17 April 2023 15:56 UTC](https://pyfr.discourse.group/t/incoming-flow-with-an-angle-of-attack/799/1 "2023-04-17T15:56:21Z")

</div>

Hello, when I simulate the supersonic case with an Angle of attack, Assume freestream velocity is U, angle of attack is the theta, then the inflow condition is u = U_cos(theta), v = U_sin(theta)? And I try this operation, the result seems wrong.

---

<div class="post-metadata">

**Author:** ![WillT](https://avatars.discourse-cdn.com/v4/letter/w/bc79bd/32.png) [@WillT](https://pyfr.discourse.group/u/WillT)\
**Post date:** [17 April 2023 16:04 UTC](https://pyfr.discourse.group/t/incoming-flow-with-an-angle-of-attack/799/2 "2023-04-17T16:04:18Z")

</div>

If I remember correctly, theta needs to be in radians. Have you tried this?

---

<div class="post-metadata">

**Author:** ![fei](https://avatars.discourse-cdn.com/v4/letter/f/59ef9b/32.png) [@fei](https://pyfr.discourse.group/u/fei)\
**Post date:** [18 April 2023 15:49 UTC](https://pyfr.discourse.group/t/incoming-flow-with-an-angle-of-attack/799/3 "2023-04-18T15:49:06Z")

</div>

Okey, I will try. In addition, can I ask another question? In a 2D case, when I calculate the wall skin friction through paraview, I use ‘Gradient and generate surface normal’ filter, then use Calculator (Density\*Velocity\_X/Re)\*GradientV\_XY, and then use ‘plot over line’ on the wall to get the data. But the result is close to zero. Is anything wrong?

---

<div class="post-metadata">

**Author:** ![WillT](https://avatars.discourse-cdn.com/v4/letter/w/bc79bd/32.png) [@WillT](https://pyfr.discourse.group/u/WillT)\
**Post date:** [19 April 2023 07:32 UTC](https://pyfr.discourse.group/t/incoming-flow-with-an-angle-of-attack/799/4 "2023-04-19T07:32:57Z")

</div>

Make a new topic and ask it there.