boit
8th January 2009 - 04:18 PM
QUOTE (rovman+Dec 10 2008, 11:06 AM)
Hello all
I understand
water is denser than air and that it would take a much higher wind speed to create the same force on a surface than water speed. Is there a way to calculate this? For instance. If 2 knots of water pushing on a 1 square foot surface area produces one force, what is the equivalent wind speed needed to produce the same force on the same 1 square foot area?
Thanks in advance
Find the relative density of air at sea level and you will have the ratio of the relevant velocities. I guess you should be on your way to get the answer. Cheers.
Chalnoth
8th January 2009 - 09:14 PM
Certainly the relative density is a good starting point, but that's most certainly not all there is to it. The property of the fluid that you want to actually use is viscosity, which is the resistance a fluid has to deformation. You can read about it at Wikipedia (still too new a member to post links).
Unfortunately, however, fluid dynamics is pretty tricky business, which basically means it tends to be quite challenging to do any of the computations easily. But you could just go by the density to produce an extremely simplified approximation.
boit
12th January 2009 - 06:37 PM
QUOTE (Chalnoth+Jan 8 2009, 09:14 PM)
The property of the fluid that you want to actually use is viscosity, which is the resistance a fluid has to deformation.
...But you could just go by the density to produce an extremely
simplified approximation.
Oh! I must have got off on a less difficult point. I thought the mass of the wind or water was hitting the square surface (say sail) head on. If we are talking parallel forces here, as in formation of dunes (by moving air or water currents) or coandas force, am afraid that is beyond me. Otherwise pressure= density*velocity squared.
Since pressure is force per unit area there is your 'simple' answer.
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