# Velocity of two-dimensional flow [closed]

If the velocity in a two-dimensional flow is given as $\vec u = \left\langle {u(y),v(y),0} \right\rangle$. Why must $v$ be constant? I am not sure where to start. Can anyone help?

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 Hint: $\nabla . \vec{u} = 0$ (the incompressibility condition) – poorsod Oct 7 '12 at 23:07 Yes, I used the incompressibility, but how do I know it is satisfied? It is not given. – glebovg Oct 7 '12 at 23:14 Assume it explicitly. You can't answer the question if you don't, so obviously they just forgot to write it in – poorsod Oct 7 '12 at 23:16 I guess you're right. – glebovg Oct 7 '12 at 23:17 Also delete the question as it is too localized. – Ron Maimon Oct 7 '12 at 23:29

## closed as too localized by David Zaslavsky♦Oct 8 '12 at 3:48

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