The liquid that comes out of the orifice forms a jet of liquid that possesses an area of cross-section less than that of the orifice. The area of the cross-section of this liquid jet goes on decreasing and attains a minimum value at a certain point. At this point the area of cross-section (Ac) is minimum, the streamlines are straight, parallel to each other, and perpendicular to the plane of the orifice. This section is called as vena-contracta. Usually, vena-contracta is located at a distance equal to the radius of the orifice.