10

Changing currents with time

If fluid currents change with time, a pressure difference is associated with the process. This phenomenon and its consequences are discussed in detail in Chapter 5.

Movie 1 shows the starting of a current of water out of a tank.

Remark

Distinguish this phenomenon from the change of fluid speed from point to point in space (all at the same point in time!) due to changes of flow geometry (such as narrowing or widening of a duct; this phenomenon is described as Phenomenon 8). In the case of spatial changes of fluid speed, the current does not (have to) change.