ItchyRivers, in principle there is no limit to Notar size. The biggest problem seems to be that Notar is not as effecient as either a tail rotor or fenestron. This is due to the tail rotor offering a good area, and using the front up rotation to gain extra thrust in the main rotor downwash.
A good starting point for your CFD sim is the momentum method hand calculation, as detailed by Prouty (Helicopter Performance Stability & Control).
The calculation gives:
Rotor_Induced_Velocity = SQRT ( Weight / ( 2 x Air_Density x Rotor_Area ) )
While the downwash velocity is 2 x Rotor_Induced_Velocity.
The basic concept behind Notar seems to be to try to force the coanda effect to keep the flow attatched to an unaerodynamic aerofoil (circular section). The practical installation seems to rely on the small cross section air jet to replace the tail rotor. Conventional tail rotors sometimes fit strakes to the boom, but not to produce any torque reaction. Instead these seem to provide a definate flow seperation point, to avoid buffeting in cross winds.
Hope that helps.
Mart
Last edited by Graviman; 24th March 2007 at 21:11.
Reason: Tidy up for clarity of equations.