For 2-D incompressible, inviscid flow, a convenient conservation equation may be derived for the z-vorticity, wz = av/ax au/ay. For this, you may use the x- and y-momentum equations: ди дх ди ди 1 др ди ди +u - +v +v + Ot ду рдх дх2 дуг αν αν +u Ot дх dv 1 др + V + ду р ду дх2 дуг After making appropriate assumptions, you should take the y-derivative of the first equation and the x-derivative of the second equation. Then, combine these to eliminate the pressure term, and replace the velocity gradients with the vorticity. a. Show that this may be written in a conservation form involving Dwz/Dt. (Hint: you may need to use the continuity equation!) b. What does your expression imply about the vorticity of a fluid element?