Fluid Flow: Type of Flow

The flow can be classified as uniform flow and non uniform flow or steady flow and unsteady flow. Uniform Flow: when the velocity is same throughout the system at any time, it is called uniform flow.  the velocity can be different wrt time.

Steady Flow: when the velocity is constant with respect to time at any point. the velocity can vary with position. 

In a water tank, water comes out of the tank under gravity, the velocity will change with time due to decrease in height of water in tank. i.e. unsteady flow but according to the continuity equation velocity will be same i.e uniform flow.

 In a venturimeter, the area changes, so does the velocity i.e. non-uniform flow. if the flow rate is constant, then the velocity will be constant at any point with time i.e. steady flow.