Turbulence modeling both addresses a fundamental problem in physics,
'the last great unsolved problem of classical physics, ' and has
far-reaching importance in the solution of difficult practical problems
from aeronautical engineering to dynamic meteorology. However, the
growth of supercom- puter facilities has recently caused an apparent
shift in the focus of tur- bulence research from modeling to direct
numerical simulation (DNS) and large eddy simulation (LES). This shift
in emphasis comes at a time when claims are being made in the world
around us that scientific analysis itself will shortly be transformed or
replaced by a more powerful 'paradigm' based on massive computations and
sophisticated visualization. Although this viewpoint has not lacked ar-
ticulate and influential advocates, these claims can at best only be
judged premature. After all, as one computational researcher lamented,
'the com- puter only does what I tell it to do, and not what I want it
to do. ' In turbulence research, the initial speculation that
computational meth- ods would replace not only model-based computations
but even experimen- tal measurements, have not come close to
fulfillment. It is becoming clear that computational methods and model
development are equal partners in turbulence research: DNS and LES
remain valuable tools for suggesting and validating models, while
turbulence models continue to be the preferred tool for practical
computations. We believed that a symposium which would reaffirm the
practical and scientific importance of turbulence modeling was both
necessary and timely.