If flow is irrotional, the relation that satisfies the flow condition is
1
\(\frac{{\partial {\rm{U}}}}{{\partial {\rm{x}}}}\, - \,\frac{{\partial {\rm{V}}}}{{\partial {\rm{y}}}} = 0\)
2
\(\frac{{\partial {\rm{U}}}}{{\partial {\rm{x}}}}\, + \,\frac{{\partial {\rm{V}}}}{{\partial {\rm{y}}}} = 0\)
3
\(\frac{{\partial {\rm{V}}}}{{\partial {\rm{x}}}}\, - \,\frac{{\partial {\rm{U}}}}{{\partial {\rm{y}}}} = 0\)
4
\(\frac{{\partial {\rm{V}}}}{{\partial {\rm{x}}}}\, + \,\frac{{\partial {\rm{U}}}}{{\partial {\rm{y}}}} = 0\)