Handbook of Turbomachinery Second Edition Revised - Ventech!

Figure 18 Aerodynamic and heat transfer results from the vane measurements of
Joe et al. [43].
Often the key to making these calculations work is the gridding scheme
chosen. Figure 19 shows a comparison between computation and
experiment of surface static pressure normalized to total pressure for the
code of Rao and Delaney [44] as compared to data taken by Dunn [37]. The
computation is made on overlapping ‘‘O’’ and ‘‘H’’ grids between which
information is shared iteratively as the solution is integrated forward in
time. ‘‘O’’ grids consist of lines radiating outward from the airfoil surface,
which intersect with concentric closed loops starting at the airfoil surface
and moving outward. ‘‘H’’ grids are lines in the flow direction intersecting
with lines from one blade surface to the next. This combination of grid
schemes gives maximum solution accuracy both near the surface and
throughout the main stream.
In these types of codes the boundary conditions must be nonreflecting
in that as the solution proceeds (converges on a periodic unsteady solution),
‘‘waves’’ generated in the solution do not ‘‘bounce off’’ the edges of the
solution grid and become artificially ‘‘trapped’’ in the grid.
Figure 19 gives the results of the 2D, unsteady, full Navier–Stokes
calculations of the surface pressure over a full cord at midspan by Rao and
Copyright © 2003 Marcel Dekker, Inc.