Dear all, I'm a bit confused about a 2D problem which I thought had a simple solution... I don't know if I'm correct, so: I have a 2D space, and time. I know the velocity field v(x,y,t). I would like to know where the particle which start at the position x0,y0 at an istant t0 is at a certain istant t>t0. My idea is: p(t)=<px(t),py(t)> dp/dt=v(p,t)=<vx(px,py,t),vy(px,py,t)> %%% dpx/dt=vx(px,py,t) dpy/dt=vy(px,py,t) %%% Then I would solve it by part...even if the solution can be not easy due to dependence on time, Ex: vx=px*t, vy=px*py %%% % %% dpx/px=t dt %px=c1*exp(0.5*t^2) dpy/py=px dt %dpy/py=c1*exp(0.5*t^2)dt etc... %%% %%% Is this answer formally correct?