A technique for modeling unsteady three-dimensional compressible visco
us now over lifting rotors in hover and forward night is described, Th
e flow solver has three modules: 1) a compressible Navier-Stokes solve
r for modeling the viscous now over the rotor and the rotor near wake;
2) a compressible potential flow solver for modeling the inviscid, is
entropic potential now regions far away from the rotor, and 3) a Lagra
ngian model for capturing and convecting the rotor wake once it leaves
the Navier-Stokes domain, Results are presented for viscous now over
a two-bladed untwisted rotor and a UH-60A rotor in hover, Good agreeme
nt is found with measurements.