Question

Which of the following represents a possible two – dimensional incompressible flow?

(a) $u=5x^{3}+y^{2} ; v=-15x^{2}y+30$

(b) $u=4x+y^{3}; v=x^{2}-y^{2}$

(c) $u=x^{2}+y ; v= 4xy+10$

(d) $u=xt^{2} ; v = xyt+ y^{2}$