Hi, I am simulating a molecular flow field by having a vacuum tunnel with 3D geometry inside. The inlet emits particles at high speed normal to the front face. I was looking for the force vectors due to the particle collisions on the front facets, and I am not sure if the “direction field” vectors would also correspond to the force. The screenshot includes the vectors on the front face. I was thinking that the vertical or horizontal vector correspond to the force on the face. The profile shown by the colored facet is the pressure distribution. Any comment is highly appreciated; thanks!
The direction vectors sample the incident velocities only, whereas the force is the effect of incident particles losing their momentum first, and then once again transferring momentum to the facet during rebound, see here.
If your incident velocity is significantly higher than the reemitted velocity, then you have indeed a good approximate of the force by the velocity vectors, which can be converted to force.
You can measure the force vector facet by facet, but not per texture cell. It could be a nice new feature sometime in the future.
Update: Discussing with Roberto, he recommended using the Facet/Explode command to divide the facet into many smaller (sub)facets, then you can use the SUM and AVG formulas (see here) to get the resulting force on a body consisting of may facets.