A fluid flow is represented by the velocity field $$\overrightarrow V = ax\,\overrightarrow i + ay\,\overrightarrow j ,$$ where a constant . The equation of stream line passing through a point $$(1, 2)$$ is

In a flow field, the streamlines and equipotential lines

For a fluid element in a two dimensional flow field ($$x-y$$ plane), it will undergo

Circulation is defined as line integral of tangential component of velocity about a _________ (fill in the blank)