The current work is based on an extension of an approach developed by
Rai and is discussed in detail by Rai [6] and Rai *et
al.* [7]. The approach is reviewed in brief here. The flow
field is divided into two basic types of zones. Inner "O" grids
are used to resolve the flowfield near the airfoils. These "O"
grids are overlaid on outer "H" grids which are used to resolve
the flowfield in the passages between airfoils. The "H" grids
are allowed to move relative to one another to simulate the relative
motion between rotors and stators. The thin-layer Navier-Stokes
equations are solved in the inner zones where viscous effects are
important. The Euler equations are used in the outer zones where
viscous effects are weak. The governing equations are cast in the
strong conservation form. A fully implicit, finite-difference method
is used to advance the solution of the governing equations in time. A
Newton-Raphson subiteration scheme is used to reduce the linearization
and factorization errors at each time step. The convective terms are
evaluated using a third-order-accurate upwind-biased scheme. The
viscous terms are evaluated using second-order accurate central
differences. The Baldwin-Lomax turbulence model is used to compute
the turbulent eddy viscosity [8]. Details of the
turbulence model, zonal and natural boundary conditions, grid
configuration, bookkeeping system, and database management systems are
discussed in Gundy-Burlet *et al.* [9].

Fri Jul 25 15:51:15 PDT 1997