Article ~ 'High-Resolution Computational Investigation of Trimmed Coaxial Rotor Aerodynamics in Hover'.
Excerpts from ~ 'Conclusion':
"4) The overall performance is well predicted for the coaxial system. The bottom rotor showed a degradation of performance due to the influence of the top rotor wake (~40% increase in power at same thrust at higher thrust levels). Interestingly, even the top rotor showed slight degradation in performance....."
"6) The interactions [of the blades on the two rotors]
resulted in a fluctuation of 5%-10% in the integrated Quantities. Such a fluctuation could be significant for vibration and acoustic characteristics. ...."
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Forks in the road.
If United Technologies had kept Charles Kaman, logical evolution (such as today's movement toward highly rigid rotors) suggests that the advantages of the Intermeshing configuration would have established it as the predominant one.
Dave