Calculate velocity inflow on a 2D surface in 3D
 

Hi,
I need to calculate velocity inflow on a 2D surface in 3D. I can vaguely recall but I 'm not too sure. i have the coordinates of the 2D surface and the velocity vector

The steps are:
1. using 2 vector on the 2d surface (v1 n v2), calculate its unit cross product vector. this new vector will be perpendicular to the 2d surface

2. do a dot product between the new perpendicular vector and the velocity vector (vel vect). tt 'll give the velocity flowing into the 2D surface.

is this correct? tks!

isn't this just the curl?

There is one step missing in the suggested process: The v1 x v2 product will indeed create a normal, but you will then have to normalize it to make it a unit normal. Only then do the scalar (dot) product with the velocity vector to have the normal velocity. The direction of the latter (into or out of the domain) will depend on whether v1 x v2 is directed into the domain or outwards.