Final answer:
Fluid velocity is greatest where streamlines are closest together due to the principle of conservation of mass.
Step-by-step explanation:
Fluid Velocity and Streamlines
Fluid velocity is greatest where streamlines are closest together because of the principle of conservation of mass. As the cross-sectional area through which the fluid flows decreases, the fluid must speed up to maintain the same mass flow rate. This is represented by the equation:
Where A1 and A2 are the cross-sectional areas and v1 and v2 are the velocities at those areas. If A2 is smaller than A1, then v2 must be greater than v1 to maintain the same mass flow rate.