1. The problem statement, all variables and given/known data I have a discrete two-dimensional velocity field (u,v). I want to plot the streamlines by finding the streamfunction ψ and from that plot the streamlines by finding the curves where ψ=constant. 2. Relevant equations In order to find ψ I then have to solve the equations (see link) $$ udy = d\Psi \\ vdx = -d\Psi $$ 3. The attempt at a solution My main issue is that I'm not sure how to integrate these two equations. Say I start with the component u at point (i=1, j=1). If I have to integrate (=sum) this along y, then I basically get a number for the row i=1. But is this the way to do it?