On the application of the principle of communicating vessels

Thread Content

This post was last edited by Catalyzing a Grain on 2017-8-12 at 17:42. The purpose of having both ends of a communicating vessel open or connected is to prevent atmospheric pressure from affecting the liquid level. If the liquids in such a vessel are considered as a single entity, then they will remain at rest when the pressure at the same depth is equal; if the pressures at the same depth differ, the liquid will flow toward the area of lower pressure until equilibrium is reached. However, if an additional force is applied to a certain liquid surface, the liquid pressure at that location will increase (and if there is gas above the liquid, the pressure of that gas will also be added). To ensure that the same atmospheric pressure is applied to both (or multiple) liquid surfaces, they need to be open at both ends. Actually, it’s also possible to seal the entire container, but the air above the two liquid surfaces must be in communication with each other (it’s as if the two containers are joined together and sealed). The principle behind containers can be explained using liquid pressure. If the same liquid is placed in a U-shaped glass tube, a small liquid meniscus AB is assumed to exist at the exact center of the bottom of the communicating vessel. If the liquid is at rest and not flowing. The pressure exerted by the liquid in the left tube on diaphragm AB to the right must be equal to the pressure exerted by the liquid in the right tube on diaphragm AB to the left. Since the same liquid fills the container, the densities of the liquid columns on the left and right are equal. According to the formula for liquid pressure, p=ρgh, the pressures exerted by the liquid columns on the diaphragm AB will be equal only when the heights of these columns are the same. Therefore, when the liquid is not in motion, the liquid levels in the various containers of a communicating vessel should remain at the same level. The characteristic is that the liquid levels in all containers are at the same height only when they contain the same liquid. If the containers are tilted, the liquid in each container will begin to flow, moving from the end where the liquid column is higher to the end where it is lower, until the liquid levels in all containers are equal; at that point, the flow stops and the liquid comes to rest. If two glass tubes are connected by a rubber tube, and the same liquid is filled in both tubes, fixing one of the tubes while raising, lowering, or tilting the other allows it to be observed that the liquid levels in both tubes remain at the same height even when at rest; this is the characteristic of a communicating vessel. Apparatuses based on the principle of continuity are widely used in practical production; for example, culverts in irrigation channels, automatic water drinkers for livestock, boiler level gauges, as well as teapots and watering cans used in daily life are all examples of such apparatuses. The largest artificial communicating vessel in the world is the Three Gorges shiplocks. static/image/hrline/4.gif Well, back to the main topic: in our daily lives and at work (on various devices), we certainly encounter many examples related to the principle of containers (devices, operations, etc.) ； So let’s all discuss this together; let’s all try to figure it out and determine whether the examples given make use of the principle of communicating vessels. Participate in the prize giveaway.