# Show that the following flow is incompressible and irrotational.

Show that a uniform flow with velocity \({V_\infty }\) is a physically possible incompressible flow and is irrotational.

For a uniform flow \[{V_\infty } = u = {\rm{constant}}\,\,{\rm{;}}\,\,\mathop V\limits^ \to = {V_\infty }\mathop i\limits^ \to \]Divergence of velocity field\[\nabla \cdot \mathop V\limits^ \to = \frac{{\partial u}}{{\partial x}} + \frac{{\partial v}}{{\partial y}} + \frac{{\partial w}}{{\partial z}}\]\[ = 0 + 0 + 0\]\[ = 0\]Therefore, it shows that it is a physically possible incompressible flow.

Also, curl of velocity field \[\nabla \times \mathop V\limits^ \to = \left| {\begin{array}{*{20}{c}}{\mathop i\limits^ \to }&{\mathop j\limits^ \to }&{\mathop k\limits^ \to }\\{\frac{\partial }{{\partial x}}}&{\frac{\partial }{{\partial y}}}&{\frac{\partial }{{\partial z}}}\\u&v&w\end{array}} \right| = \mathop i\limits^ \to \left( {0 – 0} \right) – \mathop j\limits^ \to \left( {0 – \frac{{\partial u}}{{\partial x}}} \right) + \mathop k\limits^ \to \left( {0 – \frac{{\partial u}}{{\partial y}}} \right)\]\[\nabla \times \mathop V\limits^ \to = 0\]This shows that the flow is irrotational.