Tagged Questions
0
votes
1answer
38 views
When moving something by entrainment in a fluid stream, where does the energy come from?
The particular Something I had in mind here would be air bubbles that are pulled downwards against their buoyancy by a stream of water falling down a shaft. The work required to push those bubbles ...
6
votes
1answer
83 views
In a column of rising hot air, is the velocity higher at the top?
Since the movement of the air is induced by buoyancy, i. e. there's a constant force acting on the air, so I would expect the velocity to increase during ascent, much like an object falling down due ...
1
vote
1answer
1k views
Boussinesq approximation for the Navier Stokes' equation - discrepancy
In the Navier Stokes' equation:
$\rho_0 \left( \frac{\partial v}{\partial t} + v \cdot \nabla v\right)
= -\nabla p + \mu \nabla^2 v + \hat{f}$
I included the temperature variation of density as ...
1
vote
1answer
1k views
“Troll physics”: Buoyancy for infinite power [duplicate]
Possible Duplicate:
What is the fallacy in this infinite motion machine?
Most of the "troll physics" images I can figure out, but this one has me stumped. What is broken about the following ...
8
votes
2answers
750 views
The Galileo thermometer: why do the bubbles float in the middle of the tube?
If the water were uniform temperature, it would have uniform density, so a bubble should either be all the way at the top (if it's lighter than water) or all the way at the bottom (if heavier). But in ...
22
votes
3answers
1k views
What is the fallacy in this infinite motion machine?
I realize this isn't possible, but I can't see why not, especially if you change the model a little bit so that the balls simply travel through a tube of water on the way up, rather than exactly ...
