A novel technique for the prediction of three-dimensional steady and u
nsteady viscous flows past arbitrary configurations is described. The
flowfield is partitioned into an inner region adjacent to the solid su
rface and an outer region away from the solid surface. The solution pr
ocedure uses a three-dimensional compressible Navier-Stokes solver in
the inner vortical region and a three-dimensional unsteady full-potent
ial now solver in the outer irrotational region. These two solvers are
tightly coupled and integrated simultaneously in time. This coupled a
nalysis enables efficient and accurate computation of transonic flows,
including unsteady viscous effects. In the present work, details of t
he coupling procedure are described, along with numerical validation o
f the coupled formulation. Computational results are presented for an
airplane wing as well as for a helicopter rotor in hover; these are co
mpared with experimental data and other computational fluid dynamics d
ata. The present coupled analysis requires only about 50% of the CPU t
ime needed by a standard Navier-Stokes analysis and generates equally
accurate data.