Communicating vessels

When communicating vessels or communicating vessels is called open-top, but below interconnected vessels. A homogeneous liquid is equally high in them, because gravity and air pressure are constant (see hydrostatic paradox).

If the fluid is inhomogeneous, the heights of the liquid columns behave (calculated from the contact surface ) is inversely as their specific gravity.

Applications

The principle of communicating vessels is available in various ways, such as special instruments such as the Tube level and channel level ( a level, ) with which you can measure height differences on fractions of a millimeter accuracy.

When Heber, a form of suction pump, the liquid transfer is not stopped until the tie, the two liquid levels. Siphons are down - and up again leading water lines that bridge in this way a sink. Water towers also use the principle of communicating vessels to produce constant pressure in the water lines.

With a culvert can be liquids (usually water) is passed under obstacles. Also, water lines can be routed through a valley between mountains so to build without a bridge ( aqueduct ). This technique was already known to the Romans.

Level surface and measuring accuracy

Exact words, communicating the liquid level coincides with a level or equipotential surface along which the gravity potential is constant.

However, some disturbing effects must be avoided for accurate height measurements. They include mainly vibrations of the system that make the water level fluctuate at both ends back and forth. Even small differences in air pressure ( Wind! ) or in temperature can have a significant impact depending on the type and length of the tubes. For very thin pipes or hoses to the capillary effect is noticeable.

Taking all these effects accurately detected or avoided by controlled conditions, can be measured with precision hose scales height differences over distances of hundreds of meters up to a deviation of 0.01 mm accuracy. In this way a power level on the two sides of a general flow can be compared more accurately than would be possible due to the interference of the light refraction by the moisture contained in the air to measurements on optical-based also, for example.