Which of the following is constant according to the continuity equation?
A. The rate of flow of fluid mass
B. The rate of flow of streamlines
C. The area through which fluid flows
D. The velocity of the fluid
A
Streamlines are only a construct for visualizing and solving problems. In a given time interval, the actual amount of mass flowing remains constant, implying that the fluid flows faster through a smaller cross-sectional area. Thus the area and velocity of flow may both change, but the rate of mass flow remains constant.
