Can fluids flow naturally from areas of lower pressure to areas of higher pressure?

klimatos

I maintain that not only they can, but that observations illustrating the phenomena are common.

To keep the thread from fragmenting too badly, I should like to propose the following rules of discussion:

1) Liquids shall be limited to water and air.

2) Only natural flows may be offered. Nothing initiated, modified, or influenced by man or his works.

3) The flows must be unconstrained: no channels, pipes, or containers.

4) A flow from low pressure to high pressure shall be deemed to have occurred if the internal pressure (as measured by an imaginary manometer at the midpoint of the parcel of fluid) is higher at the finish of the flow than it was at the beginning.

5) Acceptable evidence shall consist of scientifically-accepted citations and/or compelling argument.

What are your thoughts?

olivermsun

This one might be problematic. Are there unconstrained geophysical flows?

Studiot

Well it really depends what you mean by 'pressure' in the fluid.

However in principle it's simple to offer examples where fluid flows from lower pressure to higher, simply by exploiting the gravity head component of Bernoulli's equation.

go well

xts

Any atmospheric or ocean circulation where air/water descends. Gulfstream sinking in arctic seas. Föhn winds. High pressure weather area.

Bobbywhy

As for 1): Did you mean FLUIDS shall be limited to water and air?

rcgldr

Assuming by flow you mean velocity, then due to momentum, this can happen. Pressure gradients only result in accelerations or declerations, not instantaneous changes in velocity.

klimatos

Of course, my stupid!

klimatos

An excellent example of fluids flowing against the pressure gradient may be found in the field of limnology. In those parts of the world where lakes freeze over in the winter, the phenomena of spring and fall overturn occurs.

In the Fall, surface waters cool until the temperature of maximum water density occurs (about 3.94°C). At that time, portions of the surface water will sink through the underlying water until they reach the lake bottom. During that passage, the parcels of water move steadily against the pressure gradient. The pressure at the midpoint of the parcel when it reaches the bottom is substantially higher than when it started at the surface. Hence, there has been a natural flow of water against the pressure gradient.

This process repeats itself in the Spring.