Handbook of Turbomachinery Second Edition Revised - Ventech!

are discussed by a number of authors in the proceedings of the Second
Conference on Grid Generation in Computational Fluid Dynamics [75].
In some cases, however, the complexity of the physical domain can
render even multiblock techniques ineffective. For example, an analysis of
flow through complex internal cooling passages in a turbine combined with
the flow in the primary gas path poses such a challenge. To satisfactorily
discretize such a complex domain, the most effective approach would be to
apply an unstructured grid. With the unstructured grid methodology, the
entire domain could be gridded as a single block. Because unstructured grids
are not sensitive to the complexity of the physical domain, they can be
generated with much less effort, and in much less time, than is required for
structured grids.
The development of any grid, either structured or unstructured, relies
on the specification of physical domain boundaries as a basis for grid
construction. As the geometry of the physical domain becomes perturbed
during design iterations, those grid boundaries will change, necessitating
reconstruction of the computational grid. It therefore would be desirable to
tie the grid boundary specification directly to the description of the flowpath
geometry during the design process. This can be achieved by
integrating the grid generator and the CAD solid modeling software, such
that the boundary surface grid generation is performed on the actual CAD
geometry definition, e.g., a set of NURBS surfaces. Such an approach
maintains the link between the CFD computational grid and the master
CAD model as it evolves. One example of such an integrated CAD solid
modeler/grid generator package is discussed by Rout [76], with capabilities
for treating both structured and unstructured grids, in single or multiple
blocks.
Analysis Tool Performance
Turbomachinery component design efforts are almost always limited by
schedule and resources. As a result, the application of computationally
intensive CFD analysis tools may be restricted during a design. For this
reason, improvements in analysis tool performance can offer substantial
benefits. Faster solutions permit the analysis of more candidate designs
within a given time, thereby ensuring a greater chance of success in meeting
the aerodynamic performance goals of the component. Alternatively, by
performing fewer analyses but completing them more quickly, the design
cycle time for a particular component may be compressed, which can free
resources for other activities. With sufficient reduction in computation time,
it becomes possible to use advanced CFD analysis tools that would
otherwise be impractical to apply during design. As a result, complex flow
Copyright © 2003 Marcel Dekker, Inc.