Florence_NC
Senior Member
- Joined
- Sep 25, 2018
- Threads
- 2
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- 340
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- Location
- North Carolina
- Vehicle(s)
- 2018 Type R
The issue with the water hose is that a car sitting still or moving is in a continuum of air. Thus all the air in that continuum is subject to the properties of air, streamlines, flow regions, etc. When you spray water out of a jet, that water is not part of the continuum. It has a density, and thus momentum, that is orders of magnitude higher than the air in the continuum. So the much denser, higher specific energy water coming out of the jet defeats the properties of the continuum, simply pushes the air out of the way, and impacts the windshield.yes, I also notice since faster air is on top of the wing, the lines on top of wing should actually be depicted closer together, and thus the diagram is incorrect, but the caption is correct...and yes, per bernoulli's initial must equal final, thus all mass must be conserved. And yes, high pressure does want to move towards low pressure, just like higher electrical potential wants to move towards lower, and water wants to flow down hill.
the water hose analogy is to say that water should bounce off perpendicular to the windshield. yes, there are a rushing gush of water molecules trailing behind the initial once to case a "scatter" pattern, but by and large, much of the water should deflect perpendicular to the windshield; otherwise, we be all F-ed when we wash our cars correct??
Now put that car under water, where it is now existing in a continuum of water. Then stand 10 feet in front of the car and spray the water out of a jet towards the windshield. The water out of the jet is now part of the continuum of water, subject to the same laws and rules. So do you think, in the continuum of water, that the hose will impact the windshield and disperse the same way it did in air? What if you stood 10 feet in front of the car and sprayed a jet of air at the windshield, would that impact the windshield and disperse the same as the water in air?
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