5.1 Determine which of the following velocity distributions are possible three-dimensional incompressible flows.

(a) u=2y2 +2xz; υ= −2xy+6x2yz; w=3x2z2 +x3y4

(b) u=xyzt; υ= −xyzt2; w=z2 xt2−yt

(c) u=x2 +2y+z2; υ=x−2y+z; w= −2xz+y2 +2z