Hi mate. Great video again, thank you for the effort. I have an observation. From 7:11 when the mass flux is being expanded w.r.t. the fluid particle, all the velocity terms are derived with respect to the x-coordinate. Furthermore, when the velocity is being derived for both the y-direction and z-direction, it is observed that the derivative of the velocity is with respect to "u" instead of being "w" or "v". This is strange as in the figure where you have the fluid particle the opposite is happening. Then everything is defined to its respective direction. Is that an error or is that on purpose? I would expect for the y-direction: m' (S->center->N) = rho(v - dv/dy * (1/2dy)) - rho(v + dv/dy(1/2dy)). m' (B->center->T) = rho(w - dw/dz * (1/2dz)) - rho(w + dw/dz(1/2dz)). The reason why do I think that, is because I don't see the relation between the expression mentioned at the end of the slide from 7:11 and the final form of the continuity equation mentioned in 8:34, as you derived everything w.r.t. the x-direction, instead of deriving it into all three of the directions (x,y,z). Let me know, and thanks again for the great video!
