How much of lost energy would be expected on this experiment?
Let's say you have a tunnel of 1 and 10mm diameter at 50m of sea level. The length of the tunnel is 1m. At the beginning of the tunnel but 50mm inside you have 1m diameter 2 blades aircraft propeller turning at the speed of 100kph. The propeller is set up on the tunnel as you would have set up on your small aircraft, meaning to pull the aircraft forward.
Behind the propeller another propeller (exact the same propeller as the first) so that the air being forced through the tunnel would spin the propeller. The distance between the two propellers is 300mm.
Would the second propeller spin as fast as the operating propeller (motorised)? No, certainly not you would say because of friction, heat and maybe other factors as well.
How much of energy wasted are we talking about here? what would be the difference in speed between the two propellers? what speed would you expect the second propeller to spin?
2007-12-22 12:24:30 · 3 answers · asked by mades 2 in Science & Mathematics ➔ Physics
4 hours has passed by now and nobody has yet answered my question.
For better word let's change tunnel to cylinder.
2007-12-22 17:08:29 · update #1
I must say that there is no mechanical link between one propeller to another. They are totally independent from each other.
2007-12-22 18:33:20 · update #2
SORRY: THE TUNNEL DIAMETER IS 1 METER AND 10MM.
2007-12-22 22:10:43 · update #3
Just to add a few wards to the previous answer.
If the quality of the bearings is very good , the gap between the second propeller and the tunnel is practically zero and the fluid (Air) is a perfect fluid , eventually the loss will be zero.
What it means if you are in perfect conditions and leave the experiment to run for a long time the speed of the second prop will be almost exactly the same as the first.
2007-12-22 18:30:16 · answer #1 · answered by The Rugby Player 7 · 1⤊ 0⤋
Your question is fairly open, i.e., no objective answer.
First, your second blade might just rotate with the first blade. It could 'surf' the wake left by the first blade. (It would also cost the system energy).
Whether the second blade rotated with the first blade or not, it would still cause a drag on the system. But most of the system drag is the first blade because it is the one providing power. Remember lift and drag are tied together.
If you assume the second blade were just free floating instead of being sucked into the wake of the first blade, it would still be rotating close to the same speed.
Energy waste is simply system drag. Definite waste to have the second prop, but not horrible.
2007-12-23 01:30:55 · answer #2 · answered by Frst Grade Rocks! Ω 7 · 2⤊ 0⤋
a 1 mm tunnel ?
2007-12-23 06:06:25 · answer #3 · answered by eastanglianuk1951 3 · 0⤊ 0⤋