Postby BWD » Tue Dec 07, 2010 4:36 pm
Aerodynamics and hydrodynamics are both about fluids, but have lots of differences.
Many of these are due to density and the different relationships of density/viscosity/velocity in the different fluids.
If you haven't heard about the term "reynolds number" looking it up is one good start to get a perspective on some of the issues.
But to make a long story short, there are 2 obvious and important differences you might need to think about:
1. Density. -because water is so much denser and more viscous, the hydrodynamics of an object moving in water at typical boat or board speed (8-15 m/s)are more like the aerodynamics of a similar object moving in air at supersonic speed (>340m/s)!
So, part of the reason a speedboat looks like a rocket is fashion, but part is practical!
2. Air/water interface. -boards and boats are complicated because they move in both fluids at once. This is complicated, so I won't even try to explain it -leave that up to the engineers!
Those are some basic things to think about I guess. Others are how much lighter things can be in air (and sometimes need to be...), what the range of conditions of use is, how to keep control (flaps, rudders, sheeting, reefing, etc.???) depending on the specifics....
It's a very interesting area, design and engineering for ships, boats, and boards.
Now and then I try to learn a little more about it....