So, that means if I have absolutely pure water and I allow it to flow in a manner that in its journey the pressure at any point falls, the total pressure, falls below the vapor pressure of water at that temperature, that it will form a cavity. At that place it may be quite below the water surface, it may not be on the surface, isn’t it? Then, there a cavity will be formed. This is the phenomenon of cavitation. Have you understood? Now, I will give you some values of vapor pressure of water. This is only to bring to your notice how it changes drastically with temperature.
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