Mathematics and the City Water Tower

Many cities store water in towers and from these towers they run water through pipes into houses, stores, and factories. If pumps are not used, such an arrangement is called a "gravity system." If a hole is opened in the side of a tank near the bottom, the water escapes with a velocity of flow that is greater for greater depths of the opening below the surface of the water (velocity increases with depth).

The force setting the liquid in motion is gravity acting through the liquid as pressure. The flow of the fluid toward the opening is called "streamline" flow. Every particle of fluid passing a point follows exactly the same path as the preceding particles with a velocity.