The picture below shows a venturi injector.
When the water flow enters the narrower cross section its velocity increases and its pressure decreases. Subsequently, fluid is sucked (or injected) into the venturi. The injected fluid is accelerated as it moves towards less pressure. This answer says that this acceleration is because internal kinetic energy gets converted to external kinetic energy - or random particle movement is converted to organized flow.
This is plausible insofar as particles experience less collisions with other particles when they move towards less pressure - they can move with less resistence in that direction. In the end, random particle motion is converted to directed particle motion without energy expense, which contradicts the 2nd law of thermodynamics.
What's your take on this?