[讨论]流体超负压问题

午夜流星

[这个贴子最后由午夜流星在 2006/12/03 04:30pm 第 1 次编辑]

看到一则关于负压的说明，想咨询一下，流体“超负压”仅仅只是为了数学表达方便，引进的一个“虚拟”物理量，还是是真实的具有“可测量性”的物理量？
Negative absolute pressure
In normal circumstances, the lowest possible pressure is a vacuum, which corresponds to 0 absolute pressure (or −1 atm gauge pressure measured relative to atmospheric pressure).
However, if the fluid has a high surface tension, such as is the case with water, it is possible to make higher negative pressures than a pure vacuum. What is actually happening here is the water';s surface exerts a force on anything contained within the water by sticking to the surface. [color=#DC143C]If the water has gases dissolved some will form bubbles and relieve the force, but if the water has had all the gas removed it is very hard for the water to form a new surface and so a pressure below 0 absolute is possible. This is crucial to the transpirational pull which allows leaves to pull water hundreds of meters up from the roots.