Originally Posted by DJ
However, an analogy between air and water environments may not be valid due to the large differences between the viscosity of the mediums, and the difference between their velocities.
Dave, for the past 100 or so years aerodynamicists with far more experience than i have believed that as long as you get the
Reynolds number of the flow the same, you get the same flow. This comes from studying Navier-Stokes and the boundary layer mechanism (ie well established). This only breaks down at higher mach numbers, since water is
practically incompressible.
Originally Posted by DJ
Doubling an induced velocity involves more than doubling the required power. Passing air through two disks will be increasing the velocity of that air.
Yes, but if that velocity is directed rearwards it just means the rotor power is now becoming thrust. The ideal is just the you produce one laminar streamtube (which i imagine never happens).
Take Greaney's advice, then make the props teetering for insensitivity to flow direction.
Mart